Most likely it is a defensive rather than an aggressive reaction. Your baby is probably scared and feeling threatened for some reason. Have there been any changes to her cage? Are her temperatures maybe increasing now that winter is over? Or if the kids at the party were holding her she may have been stressed or hurt and made an association of being held is scary.
Make sure your temperatures are correct and your snake has lots of places to hide and feel safe in her cage. After that, patience and gentle consistent handling while things are quiet in the house should help. Make sure you're not reacting to the striking or being nervous yourself. Move around as little as possible while holding, and do your handling sessions while there's not a lot of activity from other people or pets going on at the same time.
I'm not an expert, but these things have helped me when getting my babies used to being held. And maybe don't allow the kids to hold her until you regain her confidence. And then only with close supervision, as should be with all kid+pet interactions.
I hope this helps, but I'm sure others will chime in with more advice as well.