I wouldn’t say suburban per se, but I wouldn’t say Yale or Brown are suburban either. Although right next to each other, the Pitt campus is definitely a little more integrated into the Oakland “central business district”, and CMU is on the other side of a gorge (“Junction Hollow”) with a more separated, cohesive campus.
In that sense I would say CMU might actually feel enough different from Pitt to be a contender. Again I wouldn’t be saying this if you had ruled out Yale or Brown, but if she like those schools, I think CMU might well work.
By the way, this is Pittsburgh in a nutshell. It has a very unusual topography for a major US city, and so it is broken up into all these distinct microneighborhoods, with some sort of topographic barrier (cliff, gorge, river, etc.) in between. None of which shows up clearly on a typical 2D map, although if you turn on a terrain layer, suddenly a lot of things become a lot more obvious.
So anyway, that is why Pitt and CMU can be adjacent on a 2D map, and yet be on opposite sides of a gorge, and that can make a real difference.