New partners reaction to my coparenting.

So there have been a lot of complicated situations due to my partners issue with my coparenting situation. Me and my ex only text once a week for updates, and if there is anything special.

There is going to be a happening in the kindergarden and my partner is very hurt because my ex will be there. And she ask if I'll be sitting or being next to her, I said realistically I will be close to her, because we are both there for our son, and when my son is going to perform something for us, she might end up sitting next to me, and I won't tell her to sit somewhere else or stand up and sit elsewhere myself, just to make a scene. this really hurt my partner.

I understand this situation is really hard for her, and its completely valid being hurt by this, but is it valid to expect me to change things like this ( and a lot of other things that makes her hurt and uncomfortable) or am I "right" for standing my ground on this?