It means the girl who is falling in love. The noun phrase is the combination btw Verb + 는 and the noun. Eg: 기다리는 남자: the man who is waiting 고부하는 학생: the student who is learning 춤을 추는 여자: the girl who is dancing

It means both actually, but it needs more sentences for proper translation. 여기 제나는 내가 [사랑하는 여자]야 = This is Janna [who my beloved]. 사랑하는 여자 = 사랑을 하고 있는 여자 = 사랑에 빠진 여자 = means the women who in love.