I'm surprised that ya'll are surprised that she kept quiet.
There're numerous factors:
(1) She still has the mindset that she's an outsider, and probably doesn't feel confident in assuming the degree to which Eugene has changed (even though we know he'd step in to help her if he knew she was being abused). The only reason she was more vocal about it when her brothers were tormenting her was because her parents were supporting her (and also it's easier to dominate kids than adults), but she has no support now other than her overworked brother.
(2) The aunt, as horrible as she is, is actually the main reason Eurich is doing better. Hari probably doesn't want to get rid of the one person that's keeping this kid alive.
(3) Eugene is overworked, overstressed, and probably feels guilty about not bringing Cabel back. And he's younger than Hari was before she returned to the past. She probably figures that she, as an adult (mentally), can handle the abuse more than Eugene can handle another suitcase-worth of stress. Especially when you consider the fact that Hari already experienced all in the past. If anything, the real stress placed on Hari is confirmation that her aunt doesn't care about etiquette but is using any excuse she can to abuse this child.