theory

The thing that bothered me about Tio from the beginning (or nearly the beginning) was the question how she was able to feel if she is a robot. It was never really explained at any point of the game. First off, she didn't do so before (we don't know whether she would have been able to); thus, it was obviously not intended by her creators (this is also supported by the actuality that other TIO units cannot understand her and treat her like a defective entity).

However, it seems that after you battle her, something inside her changes (or is changed). Perhaps it's because of the "infection" of Valmar's Claws is removed that she doesn't have to follow Melfice' orders anymore and asks for new ones instead, or she's jsut somehow damaged during the fight so that her memory is influenced and she therefore doesn't remember his command(s) anymore (yet this is refuted by the fact she later on asks whether she has done anything wrong for she carried out orders).

Hence, my theory is that she has an AI that is able to learn; yet that ability is somehow suppressed by her obedient system. During the battle, though, it's being unlocked - Tio's not only "received" the capability to learn, she also acquired a "free will" now because she is not bound to outer instructions anymore.

The question remaining now is how her "heart" is operating, in other words how her feelings function and are communicated to the system, i.e. "felt". Personally, I don't have an answer to this as of yet.

Of course, all of this is just my own belief because I don't want to accept that the developers have simply not spent enough time on thinking about that (which is another realistic possibility, I assume).