I'm mad at my girlfriend for buying me a chemical peel treatment
Why are you upset at your girlfriend?
I don't need a chemical peel treatment. She's calling me ugly by doing this.
Even if you think you don't need it, it is not good to be upset at your girlfriend. She was trying to be nice and if you get angry she might decide to never to anything for you again.
Nice? She's calling me out for being unattractive. What kind of nice is that?
Your gf is not trying to say that you are ugly or unattractive. She was simply trying to give you a present that she thought you might enjoy. Tell her thank you and don't turn her down or she will feel unappreciated.