Natasha comes from the Silver Age of superhero comics, a place where men and women (and only men and women) could fall in love with each other in the space of three panels. Over the years, though, the typical action heroine has sacrificed emotional for physical competency. The type has become more deadly, but also more cold, more withdrawn.
Natasha has occupied both extremes. She’s been lonely and unfeeling and also breathless and desperate— and I don’t think either is the “right” or the “wrong” way to handle her. That’s more about the quality of the story, which varies so widely it’s impossible to make any knind of sweeping statement. But I do think the contradiction in her romantic outlooks makes Natasha a much more nuanced and interesting character than she would be otherwise.
Anyway, not everyone likes the Winter Soldier romance, and there were certainly some stuff related to it that I wish didn’t happen, but he wasn’t the first retroactive love affair she had, nor the first person she’s cried over. I’m not sure what “at least lesbian” means but I think you could certainly read Natasha as bisexual. There’s also lot more flexibility in the MCU version since the amount of canon there is so comparably limited.