there are a few female characters with names. The only scene where two of them speak to each other is when Mavis is talking to her mother-in-law. I don't remember them talking about anything other than the son, but even if there was a turn-your-head-and-miss-it moment, it wasn't long enough to count as dialogue, and the mother-in-law, while a character with lines, isn't mentioned by name.

The mother-in-law's name is Linda. There are a few conversations between Linda and Mavis: In Linda's California home, at dinner in the hotel, and at the party. Nothing show stopping, but enough to squeak by.

I've updated the rating from 2/3 to 3/3.

why? When Linda and Mavis are actually speaking to one another, they're talking about the kid, who is a boy. So the rating should be 2/3. See the movie, you'll see what i mean.

At 46 minutes in, There's a group discussion with Mavis, Jonathan, Linda and Mike. The conversation is primarily between Mavis and her mother-in-law Linda. The men contribute a word (like "yeah") or a short phrase. Linda is welcoming Mavis to their home and trying to make her feel comfortable. She bought Mavis a hat and poncho, got a room ready for them, and planned dinner.