The way Regina was written in season 2 was horrible, however they managed to fix it with 303 and 309. I don’t recall that the heroes hung out with her except the awkward dinner in 210 that no one paid any attention to her, and Emma kind of invited her as an obligation, and they never forgave her until 3B.
I do agree that they have made the problems with Regina’s redemption arc better over time. I still don’t really forgive the horrible writing of it in Season 2 as well as some problems in Season 3. Also she still waffles back and forth from ripping threatening Pinocchio as a child one moment, to worry about the adult Pinocchio being murdered by Rumpel the next. To taking Belle’s heart one moment, to yelling at Emma for ripping out a girl’s heart the next. Though she has at least in recent seasons expressed some regret for the wrong things she has done. That’s something. Still i think the writing was just bad in Season 2 with regards to Regina though it is amazing compared to now, it was still the first real problem with the show and the first decline.