isn't it possible she misses her step daughter and therefore stays in some contact b/c she feels guilt for abandoning her and or wants to maintain a R with her?
For your d's sake, I'd say they should maintain a relationship. You have to protect yourself when it happens, but I don't find your ex's contacts hard to understand. But I know it's tough on you and is on every couple that has children. You are forever connected. Sorry you're going through this.
M: 57 H: 60 M: 35 yrs S30,D28,D19 H off to Alaska 2006 Recon 7/07- 8/08 *2016* X = "ALASKA 2.0" GROUND HOG DAY I File D 10/16 OW DIV 2/26/2018 X marries OW 5/2016