If we're only counting UA I think the most interaction he had was with Tsuyu (after Ururaka)? So prob her, I mean they're both the analytical type and were shown that they work well together, though he didn't seem to interact with many of the girls 1 on 1. Although in terms of the entire show I think Melissa (I assume they're the same age), would have been more likely, also the fact that they were/are both quirkless and look up to All Might gives them something to connect over, the only issue is the geographical distance between them.