I played the second game (not the DLC yet though, but I'm also looking forward to it!) and they do not mention anything about Aloy's sexuality. The second game is actually about her building platonic bonds of friendship with the people she's met (both from the first game and the second) and how she doesn't have to save the world alone (there is also a familial bond she also forms, but that's entering spoiler territory.)

I guess maybe OP meant "She is ace" as a definitely headcanon for them, not a "this was confirmed 100% in canon." That's how I interpreted it anyway.