WIBTAH if I didn't invite my mum to an outing I want to get as a gift for my brother's birthday?

Since my brother got engaged and moved out, he’s now iving with hife wife there’s been a lot of family problems between him and my mum around money but also his wedding and how she handled it throughout, he had been really hurt by her, they are not in a good place. It’s affected our dynamic with him but especially me. We all used to be so close and it’s strained. We have tried to warn her but she doesn’t listen and isn’t accountable, but she is also very traumatised. We all suffered an abusive household and although she managed to divorce my dad a few years ago, his damage is still being worked through. Before, we would all have sibling days but especially after m,y dad left she has put all her energy into kids. She doesn’t have real friends, and she doesn’t talk to her sister as much anymore. Most people have stepped back because she always asks for money. I feel like my mum has affected my and my sibling’s relationship with my brother and his wife a lot. I feel guilty because she hasn’t built a life around herself it’s all about us and so everytime we interact with my brother since he got engaged, it includes my mum especially as they now live almost an hour away. He turned 30 and we are going round next week to celebrate it at his flat, so we will have a birthday moment for him. I want to book tickets for a show for my brother’s birthday and want it to be us siblings and his wife and maybe his wife’s sister so it’s a fun sibling thing but I feel guilty because I know my mum feels left out. When I talk to her about it that we all want to hang out more, she says she understands but then when I book things, she says oh I want to come. Thoughts?