chan is not used just for girls, is more like a cuter -san, usually you use -chan for like babies, younger kids, close friends (no matter the gender), grandparents, youthful women (like maria sensei here), your lover, cute animals. Like some people call their childhood friend with -chan, regardless of gender of these, but that depend who is it anyway, some people won't mind you calling them with -chan, others would.
Kun depend where you at, in academic or workplace, a senior will refer to a junior with -kun usually, in workplaces a senior will refer to a female employee with -kun too.