Am I being too sensitive?

Have had a tricky relationship with eldest step-daughter due to high conflict dynamics but we're also close and I think she'd like to be closer but feels guilty and probably is actively deterred. We decided to invite her long term best friend to sleepover for her birthday. I texted her friends Mum to invite her (we've met a few times). She never replied but I just found out from SD that she talked to BM and arranged something separately but no on bothered telling me. I feel silly but things like this upset me so much because I try so hard to do nice things for her and so often it falls flat, or she seems disappointed or BM meddles. I'm a bit burned out and these things make me not want to bother. On her birthday last year I put loads of effort into choosing presents she would love and she asked her Dad if she could open them myself and her siblings were all upstairs in bed. It's chipping away at me, am I being too sensitive.