Partners mum practically forcing us to a 50th..

So in a few weeks it’s my partners stepdads 50th, they’re having a huge party at their house/garden. I will be 30 weeks pregnant and 2 days after my father will be having a life threatening operation, it’s also my birthday weekend so was hoping to just have a quiet meal/hotel. Before we even replied to the group message, she was talking like we are going. So we’ve finally replied and said we will be popping over for the party and explained about my dad, she has come back with ‘popping??? You haven’t seen some family in a while and one has got it off work especially’ like trying to guilt trip him(the person has got it off work regardless... not to see my partner) when we just explained that we will be calling but why we won’t be staying!!

Baring in mind he is late 20s, and she also messaged a few days ago saying ‘I’ve realised you haven’t replied to the group, you have no choice in coming lol he’s only 50once’ like what the fuck, am I in the wrong for thinking this is just weird to be telling adults what they are doing and then disregarding the reason we have given her for just going for an hour?