I'm thinking that she is actually ashamed to be half human simply because her sides don't mesh well together.
At the start she mention she wanted to get her power back to what it once was, I'm thinking that she is losing her ability to be a hasshakusama, she had the misunderstanding that it was because of peoples perception of hasshakusama but in reality its because she's human and her human half is winning over her hasshakusama half (now being imbalance).
she may actually lose the ability to change her sizes permanently as she's growing out of her hasshakusama self, this is why she is trying to get it back, the mother might be asking about sex because that may be the final thing to end the fight.
IE if she has sex she will become full human and thus be stuck at her size or maybe even fall to her true size (what ever that is)