Not really sure how to word the title but I want to provide a little context. I'm not even sure if this is the right subreddit for it but I thought I'd give it a shot.

My (18f) girlfriend (18f) and I have been dating for nearly a year and a half now. It's definitely had it's highs and lows but I always try to work through them with her. We don't live together or anything, I am currently at university and she's living in an apartment nearby. We still see each other fairly often but I can tell it's not as often as she would like. That's beside the point though.

One recurring problem we've had recently is my girlfriend's low self esteem. She will get ready for the day and she'll be fine and then it's like a switch flips and she's upset that she can never look good enough and that she would feel embarrassed going out with me. I always try to reassure her that I think she looks fantastic (it's never been a lie either), but she'll shut me down, saying that even if I think that it doesn't matter because she doesn't feel pretty herself. I really try to understand where it's coming from, like a few weeks ago she said she didn't like the way she dyed her hair and she wanted to change it. I offered to take her to the store over the weekend so she could pick out her dye and the kind of bleach she wants. She immediately shut it down and told me she didn't want to see me until she fixed her hair. Often times when my girlfriend gets into these moods, she will be upset and pouty and a little bit angry with me for a couple days. Normally, I wouldn't take it personally, but recently it's been happening nearly once every week. For 2-3 days out of every week my girlfriend will get angry with me because she doesn't feel good about herself and she shuts me out. It's been extremely exhausting because at the same time, she doesn't like it when I don't talk to her in return, and she'll feel annoying if I don't respond, leading to another 2-3 days where she would be angry at me.

I'm just not sure how to properly deal with these kinds of situations. How can I reassure her that she does look good, and avoid these 2-3 day silent treatments? It just doesn't feel great to have to text her and beg to talk to her for so many days, just for her to ignore me over something I have no control over. I want to help her feel better about herself, and I'm constantly trying to find a possible solution to her problems. Sometimes, I just try to be there for her and listen rather than suggesting but that just results in an even angrier silent treatment because she'll feel like a burden to me. I just don't know how to properly deal with these situations anymore, and it's starting to take a serious toll on my own mental health (I've had recurring minor depression for a few years now). Any advice would be greatly appreciated.