。
She's never been in love.
Literal
She [topic-は] even-once love [object-を] did experience doesn't-exist.
The pattern 一度も~たことがない ('have never X-ed even once') is the standard way to express absolute lack of past experience. 一度 ('one time') + も + negative gives 'not even once'; ~たことがある ('have done before') is the past-experience nominalization, with the negative ~たことがない completing the frame. 恋をする ('to be in love / fall in love,' literally 'do love') is one of several love-related expressions — slightly more lyrical and emotional than 付き合う ('date someone'). 恋 specifically points to romantic love; 愛 covers a broader emotional terrain.