AITA for thinking my sister-in-law shouldn't have brought my 5-year-old a gift?

Am I overreacting about my husbands sister bringing my 5 year old gifts to my toddlers birthday party? like she legit handed my 5 year old a gift when my toddler was unwrapping her gifts and having so much fun…i was so confused bc it wasnt her birthday but here she is now expecting gifts on her siblings birthday and i am so annoyed…am i over reacting? ,y 5 year old started crying bc she only got one gift at her sisters party…i feel like she did this to spite me…she said "oh i got this gift for both of them to share so i figured it wouldnt be an issue for the 5 year old to open…AITA