I don't have any real concrete advice for this but I wanted to say that I'm sorry you're going through this.
Your GC sisters are here for you!
I was always led to believe that you're not an alum of ZTA until you have spent 4 years as a collegiate or you graduate- whichever one came first. While I was a collegiate member, there was a girl who joined her sophomore year in the pledge class after mine. Although she was only 1 year older than most of the members of her pledge class, she still felt out-of-place with them. She became better friends with my pledge than her own. She switched her major during her sophomore or junior year which set her back 2 semesters. When my pledge class became alumnae members, she did as well. I was confused because she hadn't spent 4 years in the chapter and she hadn't graduated either but she was considered an alum in good standing. I'm not sure how she was granted that status but the reason for me telling you this is to tell let you know that some people are granted early alumnae status. Maybe you can get medical leave from ZTA?
I'm sure that PenguinTrax will have better answers than me!