I always interpreted Akira as being into Ayako, but never actually having done anything with it and that her sexual comments is humour more than anything, or at least something Ayako just tolerates. I certainly could say what she does to close friends without there being any explicit meaning to it, so I'm surprised how seemingly "canon" them having a past relationship is. When she says she'll never be worthy of loving her, wouldn't a past relationship mean she'd say "I wasn't worthy" or refer to anything that went wrong? I feel it's a lot more of an unrequited love thing than that of an ex.
Considering how Ayako's romantic interactions with Asuka's made her think of her late husband and not Akira would suggest to me at least that it's the only romantic partner she's had. Otherwise a same-sex relationship surely would make her think of her time with Akira?
Also, when she says "I don't mind if it's me though", I'm pretty sure she refers to letting Asuka be romantic with her? Since Akira said it's pretty cold of her, as in, allowing a one-sided romantic relationship. There's absolutely no way she'd say she'd be fine with Akira fucking her, that just doesn't fit the situation here or what she's said previously.
