LO gets fussy around lots of people

My 4 month old gets fussy or starts to cry if we take her to parties and group settings. She’s fine and then she starts to cry or is super quiet and not herself. The minute we bring her back home she’s herself again—babbling, smiling and playing. Why does this happen? We have large families so we get together sometimes and I feel like she’s just so fussy during any get together and it makes me not want to go.