How do you deal with a jealous co-worker since i got a promotion?

I recently got a promotion at work, in our high school, working with special ed. students. There is no longer a teacher in the clroom so i am the lead educational istant in there, doing teaching, scheduling ,planning and report cards. My co-worker has not been very pleasant with me since. Always has an angry look and a pout on her lip. lip. Last year we worked very well together as a team, when we had a teacher in the cl and she is just not liking the fact that i have a say in the cl. This is not good for our students and they pick up very quick when things like this are happening in the clroom. Sometimes i go home and cry, i get so stressed. I have talked to the principal about it, he came in the clroom and talked to us about roles and responsibilities and he praises me highly for my job. What can I do?