frazzled

My fiancee agreed to help me with a project that is critical to my career. She had the right skill-set and some free time, and my colleagues were all flaking on me, so it seemed like a good idea. It was probably 20 hours of work that I was asking her to do. There wasn't a strict deadline, but I made it pretty clear that there was some urgency. That was a month ago. Two weeks ago, she told me she was done, all she needed to do was send it to me. I reminded her every day, no e-mail. This weekend she went on a trip to visit her sick mother, and although she promised to send it to me before she left, she did not. Then I didn't hear from her. She later "admitted" that she had somehow destroyed 2/3 of her work, and that she would have to do it over. I honestly do not understand how this is possible, she claims that she had done the job in pieces and had it in different files, and was pasting it into one document to send to me, and accidentally saved over the finished product. I do not understand how she also managed to delete the original documents. A big part of me (and my friends concur) thinks that she is lying to me. She has been kind of flaky lately, not following through on things, but she has never (to my knowledge) in our 7 years together lied to me. I am so angry, so confused about what this means for our relationship. I suddenly don't feel like I can trust a person who used to be my closest confidant and who I felt I could always depend on to come through for me in a pinch. Our wedding is in 6 weeks. I feel like she is changing: she isolating more, having serious anxiety attacks that are making it difficult for her to do almost anything, sleeping poorly, eating badly, losing touch with her friends... at home she just feels distant and fragile, like if I bring up anything at all emotionally loaded, she'll break down into a puddle of tears. I feel helpless, I don't know what to do. She's in therapy, taking meds... what else is there?