If you do send a letter or make a phone call, I think it would be better to go through the membership advisor. If she sees things progressing too far, she can inform the membership chairman of the situation. There is no point in airing this girl's dirty laundry to people she may not want to be friends with.
If it were a matter of just not liking her, there would be no harm in her joining ADPi at another chapter. However, if she is a risk in the ways you mentioned, you have every reason to be protective of your sorority. P.S., is there any way you can let the Kappas know, too?!?
