Is it permissible to file a lawsuit for alimony against the aforementioned young man, and do the girl's rights cease if she requests a divorce?

A husband is not obligated to spend on his wife before she moves in with him and surrenders herself to him, unless the delay is due to his fault after she has enabled him to have her. In that case, she is entitled to claim maintenance. If the husband divorces her, she has all her rights, unless she initiates a khul' (divorce at the wife's instance) for something from these rights, in which case whatever she relinquished is waived.