Am I too nice?

Just a bit of background, I have been with my husband 10 years next month, been married almost 5. In that time period, I have been talked down to by almost every one of his family members. I held my tongue mostly, even when his mom accused me of having an affair with her husband. 🤦🏻‍♀️ Because I knew that it wasn’t an important enough issue to argue about. (His mom and sisters always have to have the last word in an argument and will not stop!) And before it’s asked, yes he does stick up for me and we even went months without visiting with any of them. Well a couple weeks ago I decided to invite all 9 of his siblings over for his birthday next week to have cake and I was gonna make dinner for everyone. Everyone seemed okay with it and sounded like everyone was gonna come. Til today... I messaged to confirm and his snobby sister said “it’s not even an important birthday because it’s not a “milestone””. So I said “come if you want, or don’t if you don’t want to, but every birthday is important no matter how old you are”. This is the same sister I’ve bought hundreds of dollars worth of clothes and necessities for her 3 children because baby daddy won’t let her spend any money on the kids. And I always, ALWAYS come thru for them, yet she can’t take an hour to come celebrate her brother (not even asking anyone for gifts), just their company. So naturally hubby is upset but not saying much about it. Am I overreacting for being upset about this situation? Should I say fuck it and just stop doing anything for any of his family all together?