How can I get into a prestigious college and what should I do regarding ECs?

You have a good start with 4 solid ECs and 2 leadership positions. My opinion is that you don't necessarily need much more quantity but rather focus on the quality of your ECs. Also, try to find 1 or 2 that you are really passionate about and make that a spike about who you are and what kind of person you are striving to become. The whole notion that you need 10 or 8 or 6 is completely flawed thinking in my opinion because there are plenty of applicants that get into the best schools that are just really good at 2 or 3 things. For example, being a National Level indoor rock climber or winning awards for your paintings or getting your poems published. Remember that admissions officers are like detectives so they can tell in 30 seconds whether you put 10 activities down to check the boxes off and not very involved in anything. Some of the top ECs that there are within HS is Editor of the newspaper, ASB/Class President, Pres of DECA, Debate, Model UN, or Team Captain of a Varsity Sport. If you can't get 1 A-Level ECs on your application, I would recommend that you try to find some community service ones that are like serving on an Advisory Board for your Town or City (You can find out about all those from your City Hall), or being on some actionable committee for a Senior Center, Public Library or other Community-Based Organization, if you are politically motivated, try to volunteer for a Congressperson or Senator or Mayor, etc. Be brave and creative. Also, it doesn't hurt to take some free online eDX.org courses taught by MITx, Harvard, Caltech, etc with STEM subjects so it looks like you are intellectually vital and have an innate curiosity about learning new things. The bottom line is that elite colleges want interesting students who have unique experiences and skills that they can bring on campus to augment the college experience for other interesting deserving students. If you have 10 ECs and everyone has 10 ECs then the college campus becomes a giant pool of people who are not very committed to anything nor very good at anything so no one is impressed and no one is inspired to be a trailblazer. So be a trailblazer now, and don't worry about checking the boxes off. Makes sense?

So as a rule of thumb here are my recommendations for ivy+ schools (MIT Yale Stanford NW etc)

Take as many rigorous courses as is feasible

Have a SAT or equivalent of 1470+

Have a EC specifically related your major not just Women in STEM club such as a Robotics for electrical engineering etc

I’d also recommend at least committing to be in 8 ECs for ivy+ schools (blog, another club, women empowering, church volunteer, STEM Red, another activity such as you work a retail job, another activity such as you code/another activity that you spend around about a hour plus a week for at least 36 weeks a year. I’d say for best bet have 10 quality ECs but 8 is sufficient.

You get a small boost at most schools for being a woman in stem but you may have a bigger boost if you add to diversity on campus such as religious geographical career I typically say the best applicant for diversity is a black female from Wyoming majoring in STEM as a cliche but it generally holds true.

Hope this helps! Ask me if you need clarification on something