I'd like to expand on my earlier post, Crazed. After I posted it, I wanted to go back and explain why that was the first thing that popped into my mind. But before I could do so, our IT guy came to my desk and needed to perform some computer maintenance, so I had to log out and was not able to log back in before I left for the day.
My oldest brother is in almost the same exact situation as you. When he met his XGF, she had a 5 year old daughter, who from the beginning, he treated as his own. He and his XGF were together for 13 years, and he helped raise her daughter during that time. The only difference is that it wasn't an addiction that came between my brother and his XGF, but another man (although this wasn't evident at first). About 6 months ago, his XGF kicked him out without much of an excuse other than 'it just wasn't working for her' anymore, it was her house and she wanted him out, knowing he had nowhere to go and knowing that he was struggling to get his business off the ground, so between that and helping pay the monthly bills on HER house, he had no money saved up for an apartment, furniture, etc. So he ended up 'living' at his business, which just so happens to be around the corner from HER business. Long story short, he did his best to move on, but found it hard to do when she would constantly find reasons to walk by his shop and 'stop in just to say hi,' she would text him and hint that she'd like to get back together, but then when he would swallow his pride and express interest in doing so, she would cut him down and back away, until the next time she wanted to play with his feelings. During this time, he texted her daughter a few times, asking how she was, how school was going, etc., but he never got a response. So after six months, he's finally accepted that there's no chance of reconciliation and has started taking steps to move on with his life, and now it's graduation time. Does he get invited to her graduation? Nope. I think the reason he was given by his XGF was, "That would probably be awkward for everyone (yeah, especially her new BF!), so I think it's best that you don't come. Oh, but hey, M (the daughter) would like to get her first tattoo and we thought you could do it as a graduation present to her!" Ummmm.....really?? So he's not good enough to be invited to the graduation ceremony of the girl he came to think of as his own daughter, but he's good enough to give her a FREE tattoo as a graduation present?? Nice. And of course, my brother agreed, I think partly because he's still not over his ex and can't seem to break the hold she has over him, but also mostly for the daughter, despite the fact that she doesn't seem to want anything to do with him anymore. I think he figures, well, I can be the bigger person, and at least I'll know I did right by her and won't have to live with regrets.
Obviously, your situation is a bit different, and I'm sure your pseudo-stepdaughter isn't like my brother's. I think in your case, as everyone else has said, she is just caught in the middle and has to abide by her mother's wishes. I agree that it would be a nice gesture to send a card or something in response to the announcement - then no matter what the reasoning is behind you not getting an invite, at least you can rest assured that you rose above it and did the right thing by not taking it out on the girl. I just wanted to explain my earlier post and apologize if it sounded harsh. Admittedly, it struck a nerver...it was hard to see my big brother crying after he got dumped, just as it was hard for him to watch me cry so many months later when it was my turn to get dumped. I just wanted to clarify - it had honestly been bothering me since I left work. And I'm very sorry for the pain you're in tonight. ((hugs))