。
She's in the middle of taking off her makeup.
Literal
[topic-は] makeup [object-を] is-removing [in-middle-of-ところ] [you-know-よ].
化粧を落とす ('remove makeup') uses 落とす ('drop, take off, remove') — also seen in 汚れを落とす ('remove stains'). ~ているところ ('in the middle of doing X') is a temporally precise marker — emphasizes the moment in progress, distinct from plain ~ている which can describe an ongoing or resulting state without highlighting the 'in progress' nuance. Sentence-final よ adds an informative or assertive tone — 'just so you know.' メーキャップ is a less common loanword for 'makeup' — most everyday Japanese says メイク or 化粧 (けしょう); メーキャップ retains a more professional or fashion-magazine tone.