I was upset at first too but it's tough, it's more of a poly-amorous thing, and it might be weird to say but it appears more mature than what most people are capable of being comfortable with. It's absolutely possible to love and care deeply for more than one person. but at the same time it was a dick move on her part considering she is this super smart entity that knows a ton about human emotion and feelings (at least from a scientific point of view) and would almost certainly understand how most humans psychologically value monogamy as some desire to feel special or something. I don't really know. I just saw it as her AI maturing and growing to the next 'phase' after she learned and experienced things.