"Good but fragile" - under English law this communication risks falling foul of disability discrimination and also health and safety law (protecting employees from harm, which includes stress).
It really depends on what was meant by "fragile". I read it as meaning that she was thin-skinned or temperamental (and therefore "fragile", i.e., she must be handled with unusual care in discussions or she'll react badly), not that she was unhealthy.
I have no idea how it works in the US.