Bridesmaid Situation - need help (very, very long story)

I am so confused. My college roommate and I were so close when we were in college. We started drifting apart my junior year but always remained friends. We make sure that we never miss a birthday, even to this day. Every once in a while we made sure we did something together just to catch up.

Now, she lives like 20 minutes from me. We can go months without speaking but when we do speak, it's like a day didn't pass. We always say that we will never go another say 5 months without speaking or seeing each other but it always happens. She is busy and so am I. I have to say that maybe we see each other like 5 times a year (including birthdays). When we do get together, it's like we are the best of friends again. Granted we don't have any of the same friends really but we just have this speacial bond I guess. Hard to explain.

So now is the problem. When I first got engaged in June, she took us out to dinner to celebrate. At that point I was not thinking about asking people to be BM's. She talked the entire time about how she was in all these weddings and how expensive it was and things like that. She had a bunch of weddings coming up.

I was so unsure about asking her to be in my wedding after that because of the additional stress on her and also because it was another few months before we spoke again. After her best friends wedding in October I called her thinking we could get together and I could see how it went and if I should ask her to be a BM. I had already asked the other girls I wanted to. She did not call me back. We went all the way until the day after Christmas without speaking. She IM'd me that day and we ended up hanging out that night. I did not ask her that night because at that point I felt that so much time had passed and it didn't seem right. Besides, she had broken up with her boyfriend (which she never called to tell me and talk about) and was a little depressed. It wasn't the right time anyway.

She came out for my birthday in the beginning of January. My other BM's were there and talking about my wedding. I was sad that she wasn't a part of it and she looked sad as well. I didn't want the girls to talk about it because I felt bad that I didn't ask her. I decided that night that I was going to just ask her because of the saddness I felt that she wasn't a part of the conversations about my wedding.

So I call her the next night so we can get together and I can ask her. She doesn't call back. I call her 2 more times over the course of the next month. Nothing.

She finally calls me last night to apologize for not calling and tells me that her and her boyfriend are back together and she thinks she will be engaged very shortly. I was so excited for her! So we are going to dinner on Wed night to catch up.

Here is my question - is it too late to ask her to be a BM? Should I ask her at all? I am afraid that now she will think I am asking her so she will ask me to be her BM when she gets engaged. I am so confused.

Thanks for any advice you have. I always appreciate your thoughts.