My previous GF also was asexual toward me. Later i found out that she used dating app and spoke to person of her gender. As it turned out, she was bisexual. Learnt it after 1.5 years we spent together, first i was quit frustrated and eventually broke up. Now i understand that that was her choice and couldnt do anything to change the situation. Now i live another life and learnt to deal with problem and simply move on