Anon... I can't speak to being treated differently for being a woman, because I am not, except to say that gender-equality is fashionable to pretend to know about in this country, but not much else. Unfortunately the movement has been stalled for a while, and some people have that kind of ignorant attitude no matter what (yes, I know, ignorant is not a nice word, but I won't hesitate to use it against those who want to pretend they're better because they're men, even if they are fellow students).
However, your problem with age I can relate to very well. Please do not take this in a harsh way, but you simply have to learn to deal with it. Honestly. I am 25 and I still am treated differently every day in my line of work because almost everyone else in my industry is 1.5-2x my age. It happens. No it's not right, but it exists, and often we are in a situation where we can do little about it except "roll with it", which fortunately is one of the things aikido teaches
In summary, if you fear gender discrimination, say something to sensei. As far as age, you can always discuss that with sensei as well, but learning how to deal with it on your own terms and earn respect slowly by demonstrating consistant competence may be an outstanding lesson for you to prepare for later
Good luck, and good training!