WIBTA if I ditched the workshop/self-help session that my mom signed me up for

For the past two years or so, my mom has been obsessed with self improvement. Everytime I hang with her, she is talking about a club she has joined or a workshop that she went to recently. Most recently, the one she has been sticking with is called Landmark.

Now, if you look up "landmark organization", one of the first things that comes up is about how the organization may or may not be a cult. My mom came back from an intensive weekend-long workshop, and was telling me about how "what they taught her completely changed her view of the world", and that she was no longer depressed. She has suffered from depression her whole life, so her saying made me highly skeptical of both the organization and of her ability to self-assess.

She told me that she strongly wanted to go to this thing. I expressed that I really didn't want to, and that I was skeptical of it all. She said "Anon, I really just need you to trust me on this, please do it for me". To me, this felt a bit manipulative, but I decided fine, it's just one weekend out of my summer, I'll humor her.

Now, a couple months after signing up for it, my friends invite me to go with them to Cape Cod on the same weekend. I asked if they could do any other weekend, but this was the only one that worked for all of them.

I am not worried about wasting my moms money which she used to sign me up, because she has expressed to me many times that it is not an issue, she is well off. Of course, I'd much rather go to Cape Cod, and both my friends and my other parent have told me that this is what I should do. But I know doing so will hurt my mom, and might weaken our relationship for a while. I honestly have no clue what to do.