Your guidance counselar is a sexist moron. You should persue the career you desire. There is no such thing as a male only career and many woman have a huge amount of respect for pursuing that field. It's just some dumb sexist stereotype. My instructor is a female and has been in this field for decades.
Trust your heart because another persons belief are more like their opnions and you know what they say about opinions! My girlfriend is pursuing a career in 3D animation because she's a very good artist. That's still in the field you would pland to consider. Another thing 30 is YOUNG not old. Old is when you find you car keys in the freezer. Or when you can't get out of bed on your own anymore. Like 80 is old hahah! I have seen old I was a Certified Nursing Assistant out of high school. Many would thinkg that a woman's career not a man's they would say well a man should be a doctor not a nurse of any type. Guess what many man have to be nurses for a while to afford to cover school to become doctors so in their faces. 13 of school doesn't pay for itself.
If you persue a career and you actually study hard master a programming language and know what you're talking about it'll be the best move you ever made. Right now I have a classmate who's in his 60's learning stuff just because. I say do it and the heck with the stereotypes. If you have the ambition and the you are good at what you learn you wil find work (very easily because it'sin high demand right now) and you will be much happier you did in the first place. They are just being jealous because you want to move on to something bigger and better thing they might not ever be smart enough or brave enough to persue.
Sorry to rant off like that but if women can join the military then why not computer science. My girlfriend is doing it and I feel you should too! BTW my girlfriend and I are both prior service military as well!