Stop putting up with it. Stop giving her money. Stop letting her WALK ALL OVER YOU LIKE A DOORMAT. Doing that just validates her conviction that you are a doormat, to be walked over, taken advantage of, robbed, and humiliated.
Never mind she "might not go" to the wedding -- she should be BANNED from the wedding.
Block her e-mail, while you're at it. E-mail and text messaging (which is even worse) are the two worst things ever invented, for people who want to break away from toxic people. Because the T.P. keep e-mailing, and they keep reading and getting baited, etc., etc., etc.
I highly -- highly -- recommend that you buy Angelyn Miller's The Enabler: When Helping Harms the Ones You Love." If you have a Kindle, buy it right now -- this minute -- and read it tonight; it's a short book.
Really -- AM is doing these things because you are allowing and encouraging her to keep doing them.
T (struggling with the same issue myself right now, although circumstances are very different. Enabling is enabling, and we need to stop it!)