Dumb and naive, I know.
No - it's a learning experience. An experience many people are too afraid to even consider allowing themselves to make.
But I am burnt out, depressed, filled with anxiety, and have become at times suicidal.
My quick advice - please quit now. As in -- give yourself a few days to sleep on it -- but basically, you need to turn the page on this dead-end situation as soon as feasibly possible.
Not only do none of the side factors you're worrying about (which seem to boil down to basically: what a bunch of strangers think about you) have any significance, in the scheme of things, that would justify threats to your self-esteem and well-being -- they just don't have any significance at all.
Really - 80 percent of the startup world is based on mindgames and bullshit and pure and simple rank amateurism of exactly the sort you're describing. And at the end of the day, almost none of the things they elevate so highly (like being written up in glowing terms in the technical press or blogosphere... mostly by people who have very little direct knowledge of what they're talking about) has any significance at all.
What matters is (1) your health (mental and physical) (2) your friendship and familial relations, and (3) some minimal financial safety net (which, since you haven't mentioned it as a factor... I'm assuming you have). The rest -- accolades, wealth, thrills -- I'm not saying they're completely worthless - but they just don't mean all that much, compared to (1)-(3) above. And at your age there will be an endless stream of opportunities to pursue them -- and you can be entirely certain, under much better conditions than what you're facing now.
Finally: for heaven's sake, don't worry about your reputation going down as a consequence of quitting. People quit all the time and in most cases end up looking all the better for it. What you don't want to happen is that you get fired (especially as a reword for putting up with a no-win situation like this).
Trust me - you'll feel way much better about yourself after all this is over. And you're traveling in South America, or reconnecting with your friends and family... or doing whatever it is you've always been wanting to do these past 5 years.
Grow some balls my friend. If your work (money) is affecting you on this deep of a level then you need to step back and take charge of things once again.
This was painful to read, perhaps so because the only thing standing in the way of a solution is ignorance.
Unfotunately, this kind of situations are not all that uncommon. IMHO, there is a subset of people with those qualities that are drawn to startups. Take a “vision” or a “business” person with good social instincts and loosen their ethics and values and you will get yourself a little Machiavelli.
As I see it, you have a few moves: 1) Very gently distance yourself from that person until your relationship is strictly professional. Make sure they know as little possible about your personal life or work plans, projects, intentions, etc
2) Become more social and political yourself. It sounds like she’s been running the company and you just work there - you’d need to get your voice back. Cultivate your own direct 1:1 relationships with key employees, board members, and investors.
3) Try forming a subgroup within the company that is under your control and that can deliver some kind of independent and visible result. Do good work and make sure that more people know about it. But be very cautious about how you advertise those results
4) Figure out if anyone else is noticing her toxic behaviour. Your board and investors should be very interested in keeping the company culture healthy
5) Maybe there is a way to gently prompt a financial review by the board or investors?
If you do some of this for some time you should find yourself in a better position whether you decide to stay or leave