Spoilers!!!!!!! Along with my opinion which is the only correct one. Even ones that agree with me are wrong, you fools.
She deserved to walk away at the end. Both of them. If not, they both die. It's a dichotomy. They are doppelgangers. We get both yin and yang, both equally important. Their very masculine/feminine contrast shows this. Also the way that they make love on camera shows their nature relative to eachother.
Joel had it coming. He was useless to the plot at this point anyway. His story arch was to either save humanity or her. Albeit a sort of contrived writers power, but that's it. After that he doesnt need to be in the story.
Sorry you've never experienced a tragedy before.
Abby isn't trans either. Shes just buffer than you. Don't get so butt hurt. It's also a beautiful thing that the little girl shaves her head to be like the big male fighters that she aspires to, Like a classic Mulan story.
That all paves way for our pro/antagonists to break down everything they have and know and love. To become like eachother and to truly breakthrough a paradigm shift into eachothers thresholds of morality.
Good job Naughty Dog.