Iris was a synthetic human created in a Turbotax lab, meant to spread their influence after assimilating into society.
She escaped and tried to be her own woman, but a passion for taxes is what she was made for. This is why she's so eager to help you do her taxes, and why she especially hates Turbotax (on top of the other reasons). She does love you, but helping with tax forms is the only way she knows how to express that love.
i got the feeling that she was some sorta artificial creation when i started poking around after my initial playthrough. specifically the dialogue from the library lady about her
well actually, one of the wattpad stories about her actually makes this detail pretty clear too
idk why i said i missed it, now that i think about it. ig i just didn't take it too seriously lmao