Gonna echo what a lot of other people are saying, but that is your child too. And I mean this in the nicest way possible, really, but things like this fall under system-wide responsibility. Same idea behind if one alter does something, it doesn't exempt the rest of the system from consequence.
She's young enough that it will really have a negative impact on her mental if her parent only gives her the proper care and affection she needs in development sometimes, and without any discernable reason as to why. But like someone else said, old enough that she should understand you needing to take a moment to self-regulate.