Elaine

Elaine is a singer of some fame, often on tours. (The protagonist says at one point that she is quite popular with "housewives", but no mention of what kind of genre she sings.) She is a close friend of Amy and also her boss, having employed Amy for her makeup-skill.

As there is a bit of a gap in the touring, she has come with Amy to visit Allison and the protagonist and get a bit of vacation. As the protagonist didn't know they were coming and though himself home alone, he was found skinny-dipping in the hot tub in the backyard. Elaine was quite impressed with his "equipment" and quickly started making advances, at one point flashing her enormous boobs at him when Amy was looking the other direction. (Regarding the size of her breasts, the protagonist at a later point says that they are the first pair of breasts he has seen that would be able to completely engulf his penis (during a boobjob), and he has a giant penis.)

When going to bed, she makes very clear that she expects to be looked into during the night but that she is a heavy sleeper and the protagonist will need to get "creative" to wake her up. He does visit her, finds her sleeping in the nude and proceeds to wake her by fingering her to orgasm. They than have sex in various positions. Elaine is very satisfied and explains that she can normally not indulge in one-night-stands because of gossip-journalists and the possibility of leaked sex-tapes. Here, however, she is safe to indulge.

In fact, this is what she appreciates most with visiting Amy's family; there she is no longer the famous singer, just one more in the extended family. Being treated like an ordinary person and able to relax.

Elaine has trained Krav Maga for decades and is a third degree Black Belt.

Spoiler

(In fact, she was the one who rescued Amy from an assault 23 years ago. She was quite skilled already then. This was what started their friendship.