Evil Step-Mother (to Be?)

Tomorrow is my son's birthday. I gave his dad a chance to come see him.. he wanted to bring his fiancée (we're still married) I said no. So he finally said he would keep her away while he visited the boys and would just have his cousin come as a"witness" the thing is the boys and I were the ones who has been abused by him so why don't does he need a witness? To make matters worse he had a blow out and needed to be rescued.. I had no problem helping him but was hurt by how surprised they acted to my saving their butts.. anyway low and behold he got her name TATTOOED on his arm. A point they both made sure to emphasize before we left she said " did you see his tattoo?!" Then stuck her hand in my face "and look at my wedding and engagement rings!" On a side note he NEVER bought me an engagement ring and only got cheap crappy wedding rings for me (which was fine for me... I loved him)but worst of all he hasn't given me a dime for his sons while he's blowing $on her left and right. They got him a POS piggy bank as card which she signed MOM.... How do you think cheating with my husband and seeing MY children ONE TIME makes you their MOM!?! No. I hate this. Why would she or he for that matter think this is ok?!