Lesbians: Do you have a problem with guys hitting on you?

A young woman I work with is a lesbian, and is in a relationship with another woman (both are in their early 20’s). They have been dating for about a year, but do not live together. My co-worker shares a house with three other woman, who are not lesbians. She is constantly being hit on in her home by either her housemates’ boyfriends, brothers or friends who come for parties. She sometimes wakes up in the middle of the night to find a guy sitting in her bedroom.

Confronting the roommates and the young men, she gets answers like “He’s Christian, he wouldn’t do anything creepy like that” or “are you sure you weren’t coming on to him?” or “are you sure you’re really a lesbian?” or “you just haven’t met the right guy yet.”

Is this a common problem?