。
She kissed me passionately.
Literal
She [topic-は] intensely me [to-に] kissed.
はげしく is the adverbial form of the i-adjective はげしい (激しい, 'intense, fierce, violent') — built by swapping ~い for ~く. The adjective covers physical violence, emotional storms, weather extremes, and passionate behaviour, all unified by the sense of unrestrained force. キス itself is a loanword that long ago became fully naturalised; combined with する it functions as a regular verb. Notice that the recipient of the kiss is marked with に, not を — Japanese treats kissing as a directional action toward someone rather than a transitive operation on them.