Well, if the Radio Drama is anything to go by, she spent her remaining life caring for Alucard and showing him that he need not be like his father, resulting in him not going back to an eternal sleep again, but staying awake, fighting his father for centuries to come, resulting in him becoming Genya Arikado in modern times.
If there was any actual romance between them however, remains up in the air. A popular fan theory suggests that Alucard and her founded the Lecarde bloodline, but personally, I think that's not possible. In any case, I think her adventuring days were over after the Radio Drama, or at least low-key enough (for a Vampire Hunter) to not warrant another game starring her. Who knows, maybe she would have made an appearance in that cancelled game starring Alucard?