。
She's been dyeing her hair black for years.
Literal
She [topic-は] how-many-years-even-from-前から hair [object-を] blackly is-dyeing.
An interesting set of pieces. 何年も前から literally 'from many years ago' = 'for years now / for years past.' The pattern 何 + counter + も + 前から is a productive way to express duration extending into the past from the present. 黒く is the adverbial form of 黒い ('black'), used here to specify the result-state: 染める ('to dye') takes the resulting color in く-form (黒く染める = 'dye black'). Add ~ている for the resulting/ongoing state of the dyed-black hair, and you get a description of long-running personal practice.