Michelle is one of the three girls that are studying the folklore of Romania. Out of the three, she's the one that Stefan takes notice to the most; perhaps it's because she the only one of the three that actually exhibits real intelligence. (But then maybe that's just me) Likewise, she shows a strong interest in him. (Well? Can you blame her?)
When both Mara and Lillian fall under Radu's control, she refuses to leave them because she still believes that there is a chance that they're still alive. She refuses to give up on their friendship so easily.
This, of course, is what leads up to Radu biting her and Stefan turning her.
I really don't like the following movies, but I suppose that could be attributed to Stefan's 'untimely' death within the first couple minutes of the second film. But despite my anger, I'll tell you what happens to Michelle.
After being turned, Michelle is extremly lost in her world. She realizes she isn't the same person she was before; in more ways than one, of course.
For the couple of days after she has been turned, she is the sole possesor of the Bloodstone, but is very nervous to use it. I think it's just because she's afraid of what she'll become if she admits she needs it or something.
Radu soon comes to reclaim the stone, and unsuccessfully tries claim Michelle as his loyal fledgling. (HA!) Now without the stone, Michelle is left with no other choice but to go out hunting. She hates the thought of hunting humans as though they were animals, but once she gets to the point of actually doing it, her vampiric side takes over and she bleeds a man dry. (very sick scene, in my opinion)
Radu catches her soon after, and it is here when her self loathing really begins to come into view. When her sister Rebecca comes to save her, she begs and pleads with her to kill her. Rebecca has no intention of listening to her sister, and Michelle cannot bring herself to go through it with it on her own.
On their escape from Castle Vladislas, Rebecca and the embessy guy Mel both die in a car accident. Michelle survived because of her vampiric ways, duh, but she is still lost and now completely alone. She ends up in a monestery that was converted into a hospital, but it isn't long before she gives up her protection from Radu in order to save his life. Don't ask me why, she just does.
By the end of the series, Michelle is hanging around with Radu, but still desperatly wants to just end her life. Her new friend Anna is put in danger at one point, and Michelle takes great joy in finally helping finish Radu off once and for all.
At the end of the last movie, Michelle is now owner of the Bloodstone.
