。
She has never been in love until now.
Literal
She [topic-は] until-now-additive once-also love [object-を] did [experience-こと-が] not-exists.
一度も + negative is the workhorse pattern for 'not even once' — 一度も食べたことがない ('never eaten'), 一度も会っていない ('haven't met once'). The も is what flips it from a positive count to an emphatic negative; without も, 一度 just means 'one time.' 恋をする ('to fall in love, to be in love') is one of several romance-vocabulary collocations: 恋に落ちる ('fall in love'), 恋愛する ('be in a romantic relationship'). The full pattern 今までに一度も~したことがない is a fixed superlative-negative scaffold.