I COMPLETELY disagree with everything you just said. Yes, my friend might have been referring to herself and not me, but I am in NO way invalidating myself. Mental illness is just as serious as physical illness. If you have diabetes, you have to take insulin, otherwise you could have serious consequences. Mental illness is the same way. The consequences might look different, but it doesn't mean it's not serious. It's extremely difficult to function or get by without medication. If I weren't taking meds, I probably would not be able to hold down a job. I've tried the no meds thing, and it went very badly. It's very invalidating when people make ignorant statements about "getting over it". People with mental illnesses that aren't as severe or the can be managed without meds should definately try not to depend on them, but some people don't have that option. You have the right to believe whatever you want, and I have to right to disagree.
Mental illnesses may cause issues with the way you think, but it is NOT all in your head. When people say that, they're saying it's made up or not real. That is NOT a judgement you have the qualifications to make. Being told that something you struggle with is not real is very invalidating. My Bipolar disorder, PTSD, BPD, GAD, Anorexia- are all very real and troublesome. No one can tell me otherwise, because they are not me. We can agree to disagree on this.