。
She likes soaking in hot baths.
Literal
She [topic-は] hot bath [in-に] soak [nominalizer-のが] like is.
好きだ ('like') takes が, not を, for the thing liked — a famous case of an adjectival predicate selecting が. The whole proposition 熱い風呂につかる ('soak in a hot bath') is nominalized with の and that nominal serves as the subject of 好きだ. 風呂につかる ('soak in the bath') is a stock phrase, with the bath marked by に as the location of the soaking.