I think it's just emotional abuse, not a curse. I remember when I was about Hydra's age (12-ish?) when my dad, whom I idolized, was disappointed in me, I wouldn't eat anything other than what it took to make people think I was okay and whatnot. Self-punishment, it's a nasty thing. (Yes, things got better once he found out that what I was doing.)

I don't doubt that if Bellatrix was truly upset she'd go for some small cursing, but nothing that'd actually hurt Hydra's health. She does love her daughter, but it's the same love she's got for everything/body that isn't the Lord Protector.