Tama's mom was 100% correct
Try 50% correct. While what she said wasn't exactly
wrong on a technical level, its not the kind of thing you say to someone going through suicidal depression and was making a cry for help. The whole mentality of "grit your teeth and bear it" and trying to trivialize struggle as just being "part of life" is one that is very damaging to a persons mental health, and makes it feel like they aren't being seen for what they're going through.
It's why what Rentarou tells her is so important to Tama: he's not invalidating her feelings, he's recognizing that she, like everyone, has
limits to what she can go through, and that everyone's threshold is unique and should be treated as valid.
It's also what makes Tama's decision to find a part time job even if she hates working an important moment, her threshold has
changed because she now has something in her life aside from the soul crushing monotony of going through the motions: she has someone who sees her and is willing to be there when she needs him.