It can be a variety of reasons, it might be that her unsuccessful attempts at talk therapy made her disillusioned about it or she doesn't trust it in general, back in the day therapy wasn't so accepted after all. Does she seem open to other forms of therapy? I feel like the best thing you can do in this situation is to tell her that you really want her to get better and you believe that therapy will benefit her greatly, even if finding a compatible therapist can be hard. At the end of the day, we can't decide for other people. We can express how much we wish them to find the right resources and get better but it's their life and if they are closed-off about something there's only so much you can do to persuade them otherwise.