(((iamspecial))) - firstly I'm very sorry you're not feeling well physically and very upset emotionally. Family stuff and grudges can really get out of hand. This is how I would handle it. First off, your aunt sounds extremely immature and selfish - she needs to stop acting like a kid and be an aunt. I'm happy your friends husband is doing better with the cancer and they're going to making this last pledge of love. This is their day....not your aunts or anyone elses. Your friend asked you to be in her wedding, therefore you should go and participate. That also goes for any other family function where your aunt is.

Tell your friend to tell your aunt - ["this is my special day and I won't be given an ultimatum. You (the aunt) is welcome to attend, if she can put aside her differences for that time and I(the friend) won't be forced to choose between you and my friend (iamspecial)"]. You should have a talk with your friend and tell her, you want to be her bridesmaid and no one will ruin this special day for them.

I know family problems can be draining, but try not to let an immature person like this make you not want to live. On the day of the blessing - practice mindfulness and say over and over in your mind - this day is for your friend and her husband...not your aunt". Whether your aunt chooses to go or not is up to her. Pass the ball to your aunts court and hopefully it will hit her in the head and knock some sense into her. In the meantime - I'll be sending positive vibes and sending some "go girl attitude" to you. Hold your head up proud, enjoy that day and support your friends.