Am I in the wrong

I don't have the best relationship with my mum we haven't spoken directly for a year she changed her number and didn't tell me. We've been speaking through my sister who lives at home Getting married in a few months and decided this would be my last chance at having a relationship with her if she makes the effort to come as she's missed so many other important life events. I sent my family the save the date last summer and the invitation in January it's been over a month since rsvp were due and I had to chase them all got answers from everyone except my mum. I text my sister to ask if mum was coming and she said no she doesn't think she will be coming to then gave a number of excuses the Frist being she can't walk far so I said she could use a wheelchair in which I was told they don't know where to get one and even if they did she wouldn't use one. Then another excuse of she now has travel sickness and her medication will wear off and she will be asleep by dinner time I called her out on it being bullshit excuses if other much older relatives with severe health and mobility issues can make the effort she can. I said if she doesn't come to this then I'm going no contact as she doesn't bother with myself or my children and hasn't for years Today I get a text that she is looking for an outfit I replied I'm confused is this what the problem was? Now I'm being told it is the cost of all of it I don't think that this is a good enough reason when they've known about the wedding since August last year could have been saving for it already, most people would do whatever possible to make sure they would attend their child's wedding. She would be able to share a travel expenses and we've offered for her to stay at our house the night of the wedding as we won't be home but that's a no too Am I wrong for not thinking this isn't right of her?