should I be offended by my MIL

My partners 40th birthday is coming up. When I was at my MILs house she casually brought up that she had a conversation with my husband's good friend about throwing a surprise birthday party for him. I was taken aback bc I was not included in this conversation and I quite frankly, felt hurt and disrespected in a sense. I appreciate the gesture/offering but felt like this was a bit out of bounds. I wasn't sure what she wanted me to do with this info so I asked her what she wanted me to do. She said she can get the friend to invite most of the people but there are a handful of ppl she can't reach so she asked me to contact them. I guess I'm still feeling some kind of way and wanted to see what others thought or could relate.