。
She has gaudy makeup on.
Literal
She [topic-は] poison-poison-like makeup [object-を] is-doing.
毒々しい is a productive ADJ-ADJ-しい construction: doubling 毒 ('poison') and adding ~しい to derive an adjective meaning 'gaudy, garish, lurid.' The poison-imagery captures the harsh, almost sickening visual quality. 化粧をする ('put on makeup') is the standard verb-noun pairing.