。
She's in the middle of bathing the baby.
Literal
She [topic-は] baby [object-を] bathing-is [in the middle of-ところだ].
入浴させる is the causative form of 入浴する (to bathe): 'to make/have the baby bathe' = 'to bathe the baby.' The ~ているところだ pattern means 'is right in the middle of doing' — ところ literally means 'place/point,' and here marks the temporal midpoint of an action. This is distinct from ~たところだ ('just finished') and ~ところだ (about to).