I don't think it possible to over-analyze how AIs can desire humans. (Or anything else, for that matter. There is no over-thinking, only sometimes under-acting.) What we are really doing when we do that is trying to imagine what Bubbles is feeling.
First off, we have to keep in mind that AIs who consort with humans are a self-selected group who like to talk and make friends. We know, from a throwaway joke, that some tried to consort with dolphins, and that this did not work as well. There are likely a great many AIs for whom humans are a peripheral concern. Bubbles, by contrast, is naturally inclined toward friendship.
Second, Bubbles is bereaved, bereft of her memory of bereavement, and trying to make friends again anyway. She is risking much more than any of the other AIs, and so is bringing a much more intense mixture of fear, desire, and determination to the table.
Third, Bubbles has grown up immersed in our culture, in which sex and romance are continually upheld as heaven on earth, because they just about are, and because they can be used to sell you just about anything.
Fourth, Bubbles in particular must have some way of gearing up suddenly from everyday life into combat mode. It would be absurdly wasteful to have her continually able to knock down walls and overturn armored vehicles, and would lead to accidents every time she got distracted. She must have some set of systems that do the same work that adrenaline and the related stress hormones do in humans, and arouse her body to its full capacities.
Much has been made of how close human fear-and-flight arousal is to human sexual arousal, particularly in the shy and inexperienced. The mouth goes dry, the hands get shaky, the skin flushes or grows pale, the heart stumbles and pounds, one feels hot, and so on. We have seen something like this happen when Bubbles vents coolant.
So, I suspect that what is happening here is that Bubbles is being slain by Faye's beauty, just as one of us might be slain by beauty, because we all learned how to do that from the same books and movies. At the same time, I think, her body is furiously preparing itself for some emergency, with utterly no notion of what the emergency might be. We can't know just what that feels like, because we don't have bodies anything like hers, but it is likely profoundly moving and neither entirely pleasant nor entirely unpleasant.