I see a lot of parallels your story and what happened to me last year.

Basically she is married, and that is the end of that. Certain details inside her marriage don't really matter, until they break up.

As for your relation to her, I see how you can help each other study (though it comes down to you helping her). But I wonder about how you know so much about her marriage. Now maybe I am a very private person, but to me, just studying together doesn't mean you naturally talk about these things. It seems she needs you for more than just academic support. And if she vents her frustrations about her husband at you, all I have been told that is not a very good position for romance to develop.
Furthermore, in my confusing interactions I have come to the conclusion that women are not very naive, it does seem she is either naive, or using you.

You are helping her.
She needs you for emotional support.
She knows you like her (just a postulate)
.
What does she offer you in return? I mean, I know it doesn't work that way, but she must have some ideas about the nature of her relationship with you.

I guess all you can do is help her, feel good about that, and when you see each other for the last time, tell her you like her/are romantically interested, and that she can contact you if she ever becomes single. Something like that.

Is the fact that she complains to you about her husband (assumption based on how much you actually know about it) a good sign for her romantic interest in you? I guess not.

You can tell her that you do not want to hear her talk about her husband. And that will either cause her to be confused or to understand immediately the why to it. But maybe that's not the best way for her to learn about your feelings.