Alphys doesn't look too different from her Undertale counterpart. She still wears a labcoat, though it is stained with blood. Her glasses are also cracked, which she doesn't seem to notice.
Undyne is one of the few people Alphys has a close relationship with.
Alphys loves how confident Mettaton is and how he takes care of his family. She also enjoys his snarky gossip when he comes in for repairs/upgrades or just to check up on her.
In the Genocidal Storyline, Alphys tends to be more on-edge.
At first, Alphys is scared of Lucario, seeing as he wears a straight jacket. But, after a short conversation with him she finds that he too is interested in anime. This gives him a good reputation with her, and the two regularly hang out to watch anime in Alphys' room.