『』、。
'Nice guy' is the word girls use to describe a man who won't become a romantic prospect.
Literal
''Good person'' [quotative-とは], girl [topic-は] love-object [locative-に] not-become man [object-を] express [time-時] [locative-に] use [possessive-の] word is.
A wry observation about language. 「いい人」 ('good person') is notoriously the friendzone word in Japanese dating vocabulary — a woman describing a man this way is signalling he won't be taken seriously as a romantic interest. ~とは is a topicalizer for definitions: 'as for X', 'when it comes to X'. 恋愛対象 ('love object, romantic interest') is a standard noun. The relative clause 女の子が恋愛対象にならない男 stacks a subject-が clause modifying 男.