Well there were plenty who thought she might be trans when the game came out (she's not, she's just swoll). Bigots hated her initially because of that.
Then there were people that hated the character viscerally because of what she does in the game
The game makes you feel the rage and intense desire for revenge and then smacks you across the face for it. The message is clear. Hate begets hate, revenge propogates revenge. The only way to find inner peace is to break the cycle. And it does it in a very visceral way. The game forces empathy and compassion on you whether you like it or not. And many people did not like that. Many people were absolutely furious that they were expected to step into the shoes of someone that they hate, to examine and question their own hatred, and to sort out the complicated feelings they have over someone that they condemned to death for their crimes also being a friend, a lover and a savior to other people. They could not or would not process those feelings as the game designers intended, and so they doubled down on their hatred of Abby AND of Naughty Dog/Neil Druckmann for expecting them to.
Then there were plenty that were just happy to hate a game featuring predominantly female characters, a trans character, and with a pro-compassion message.
TLOU2 was a peace of art, as was TLOU1. And the message, while not subtle, is masterfully executed on and makes you truly examine your own impulses and hatred. I love these games.