I think some cis women HATE talk of changes on hormones because back in the 50s and 60s people pretended that all differences between men and women, and I mean all, from gender expression, to things like choice of profession that were mostly the result of a patriarchal society and not innate desire or ability, were down to "the glands" (the organs that produce hormones). In your mother's mind, perhaps accepting that testosterone rules muscle development is akin to saying that women's ladybrains aren't good enough to be doctors or CEOs. Maybe explain that T is vital for stuff like fat distro, muscle growth, and sex drive but has not much at all to do with cognitive ability, personality, or, heck, even gender expression (except in utero, when that gender expression tendency is being laid down).
The biggest differences I've noticed pre and post T all have to do with sex, not surprising because sex is what divides men and women. We aren't very dimorphic when it comes to brains, sorry male chauvinists! That's not to say I'm not calmer on T because my gendered brain doesn't run well on E and progesterone, just like most MTFs are twitchy and anxious on T and calm on E, for the same reason but in reverse. But that little fact has no implication for cis people other than that they are fine sticking to their assumed hormone settings and would gain no advantage--and would probably be twitchy as all get out--on opposite hormone levels.
