Am I wrong to be mad?

Long story short. My daughter turned 7 in lockdown (August) , my husbands mum ( her nana) said can I do her a party because I didn’t get to see her on her birthday ? We thought it was a lovely idea. So anyway she is short of money. So asked if me and my husband can do everything. Again we said yes that’s fine. We hired a bouncy castle ( over £100) all balloons/decorations with the number 7 on it. A cake we had make (£45) and all the food again £100 so we’ve spent a lot of money on something she originally wanted to do . Anyway today is the day of her party. She didn’t know ! We’ve turned up and I’ve said happy late surprise birthday baby . Only to be told by everyone there !! That her nana has decided that she is doing this party for her other FOUR grandkids who’s birthday where in March !!! And I’ve brought number 7 balloons one kids is 2 the other is 5 and the other is 6 ! So I’ve paid for all this . She just said “ oh by the way we will use your cake and they can each have a turn blowing out the candles and your daughter can go last because she is the eldest and understands more”

Are you fucking kidding me !!! I’ve spend all this money on a party for not even my kids and your telling me she can’t even have her cake first ?!!

No she is ! No one understands why I’m upset and angry !!

If they all chipped in ok, if I knew a week or so ago, ok . But I’ve just walked in and found out !! 

I’m honestly fuming 😤