I doubt she is even close to 30 yet.
She's 27, which I'd call "close to 30," but of course YMMV. I think her maturity compared to the other LIs adds a few years, in a good way. So yeah, I think she manages "appears to be 30," if a young-looking 30.
Now, why she was promised to Brian when he's 9 years younger, no idea, and definitely a good question. Maybe we'll learn more about this later on.
But on the moms: Sara's mom Lily is quite attractive. So are Cassandra, Akane, and Eleanor. Hell, so is Mrs. Russell, even if she has serious RBF in the bio. I'm not interested in any of them, and I don't think the story's going that way in any event, but I think any of them could be considered a MILF.