I don't think Momo and Sam ever did "hang out", just that they were thrown together at a time when Momo was still finding her feet. Sam clearly doesn't wander about independently.
It's stated on various occasions that AnthroAIs (for want if a better term, to distinguish them from sentient fork trucks or obvious AIs like Pintsize) are more-or-less human in appearance but easily distinguished on closer inspection. Momo intermittently shows an articulation seam around the neck, but looks pretty much like a girl with pink hair and eyes; but the other ones don't.
Sam wouldn't care in-context because children can be very accepting and Momo would be a new, exciting acquaintance. The older characters treat her as more-or-less human (Faye clearly doesn't, for example, by looking under Momo-tan's skirt out of curiosity, throwing Momo-tan in the air and being openly dismissive of holo-May's details, without knowing May's views on the issue) because that's the background scenario.
This is just another convention to allow the plot to progress; after all, Dave Bowman treats HAL as a crew-member although he is well aware that HAL is an AI, and Starfleet crew treat Data and The Doctor as crew although they are well-known not to be human. Arnold Rimmer gets "upgraded" to "hard light" because the plot requires it.
But how "human" does Momo really appear? Good question. As far as can be determined, AnthroAIs have visible articulation seams unless covered by a synthetic skin. This seems to define them as having rigid, or semi-rigid exoskeletons - clearly they can articulate their faces, because (again) the plot requires it, or the artist finds it useful. On that basis, they presumably move like Buzz Lightyear, rather than Arnie the Terminator. We don't know how they actually speak; I suspect they look like the on-screen robots in "I, Robot" when they speak. I don't know what Momo's voice sounds like but I suspect her formal speech patterns sound rather like an automated on-line answering service.
All in all I'd say they are sufficiently "different" to enable them to keep out if the Uncanny Valley