Sister

So I'm not even going to get into the details of all the legalities hubby and I are trying to understand while we vie for my niece (our niece?). I'll just take this post to tell you a little bit about her mother and the type of woman I think she's become.

She's always been attention-crazy, dramatic, and selfish. She used to have better qualities, and I still love her a lot more than I probably should, but for now, I'm going to expound on these. Last night, I jumped to the conclusion that she was going to kill herself. She had been having suicidal thoughts during the day, and she called and left me a message about how grateful she is for what we're doing for Mimi, and she really sounded rather... prepared to die, kind of. I freaked a little. I called brother's house phone two or three times, then bro's cell, and still no answer from either of them. So I gave it a minute, and I called my mom. I said "This might be a false alarm, but I'd rather it be a false alarm than genuine and me ignore it. I think Cin is gonna try to kill herself! I can't get ahold of her, and I've called a lot and no one is picking up and you know Bro isn't always very observant and" in the middle of this jumble of words, Cin called me back. I told mom "That's her, I was wrong, I'm so sorry to disturb you" and switched to Cin.
Cin answered and said something about phone tag (but I'm pretty certain she was on the phone with someone else and just lied to me), and I burst into tears. Cin freaked. "What's wrong? What happened? Are you crying?" and I answered "I t-t-thought you were gonna kill yourself!!!" except I was sobbing (and Hubby says I have a very strange way of crying) so she didn't understand me. I tried again, but her only response was "I can't understand you! Please stop crying! Why are you crying?!" and I was so out of my head that I tried to hand the phone to Hubby. "She can't uberstan be, transrade!" but he didn't catch on fast enough for me, and I tried again. "I thought you were gonna kill yourself! You left that goodbye message on my phone, and you weren't picking up!"
She finally got it. She said she was sorry, that she had had a really hard day, but she wasn't trying to kill herself, everything was fine, would I PLEASE stop crying, she HATES it when I cry.
I couldn't stop. I think I was so relieved to be wrong that it was like a lever was released. I finally admitted that I had been scared to go for my niece because I thought my sister would feel free to kill herself if I did. It took a while, but she promised on our bond as sisters that she would get help and she wouldn't kill herself, and she loved me, she loved that I was going to try for Mimi and eventually we hung up. Hubby says I cried for fifteen to twenty minutes. I don't know if that's accurate (I certainly wasn't counting) but if it felt that long to him, I'm sure it felt longer to Cin. Because she KNEW she was entirely responsible.
If she weren't so flippant about saying she wanted to die, if she weren't so dramatic, if she didn't seem so easy to lose against herself, I wouldn't have jumped to that conclusion. When we hung up, I felt really good about the conversation. She would get help, she knew how much I cared if I would sob into a phone like that, and she would try better for me and her daughters. ....Hm.
Today, I got another phone call. This time she said something along the lines of 'Don't worry about me, worry about your own life, I love you, I'm so sorry for the trouble I've caused you, I'm alone in this hotel, don't worry, I love you, goodbye.' .....Weellllll, that sounds like a cry for help to ME. SO of course I tried to call back, but it wasn't happening. So I texted Chris to know what was going on. She said that Cin told her to tell me to not worry, everything is fine. Even as I began to worry, I started having niggling thoughts. Had my crying given Cin some morbid satisfaction, and made her feel really loved and as though I were really paying attention to her, to the point that she would now play on it? Would she really attempt to manipulate me so much? Well, .....yes, she possibly would. I hope I'm wrong and she wasn't doing that, but I will never know for sure.
Anyway, since I was worried, I texted Chris to call me. Right Now. Of course, she did. But so did Mom. (They both used a phone, since Momma has a house phone) I didn't realize it at first, and so I was confused as to who I was talking to when they took turns speaking in the beginning. When I figured it out, Chris explained that Mom demanded to be in on the convo, and had Chris call me so she could know what was going on as well. I demanded on knowing what had happened in the last day or two (because Cin mentioned something about my probably having heard a hundred different stories about last night and today), and Chris put me off, telling me I didn't need to know, I didn't need to worry about it. Like hell. They both doubleteamed me, telling me it wasn't something for me to worry about, and giving hints. The final story, according to them (but I'm not to let on that I know any of this to Cin) is that Cin has been doing cocaine for a while now. When she comes off the high, she starts getting depressed and talking about killing herself and then she gets another fix and is fine again. They hypothesize that Cin went to a hotel with someone for the drugs, and that's why she's way out there.
Something doesn't fit though. If the cocaine makes her feel right (and I think she's turning to drugs to self-medicate her bipolar disorder/schitzophrenia/PTSD/Depression/etc. She's diagnosed with all of those.) then why did she still sound so weepy and depressed on the message she left me tonight? I mean, maybe she wants attention like I first supposed. But maybe she's trying NOT to take the drugs, so as to keep from disappointing me again, and it's tearing her up and making her feel awful not to be on them. And then maybe she's at the hotel (she told me where she was, which is impressive enough) to gain a little perspective, maybe she went for drugs and realized she didn't want to keep doing this, and she's trying to find the strength to stop. If so, my belief in her is totally necessary, but I can't help having doubts. I really, honestly, wish I had a lie detector that would tell me the truth no matter what she tried to say. Unfortunately there's no such thing, so I'm SOL.
What do you think? What should I believe? Is there anything I should do?