I hate comments like this because it’s almost implying things like this aren’t said to black people or if they are people get angry about it and a massive deal is made about it. No, comments like this are made often re. black people and others don’t bat an eyelid.
I assume they are both white so a white person saying “you’re so black” to someone who is non-white is not the same thing.
For the record I don’t agree with her friend and think she sounds massively unpleasant but she’s not racist, if she (assuming she’s white ) would’ve said it to a black person it would have been racist hence the outrage so you’re comparing apples and oranges.
A more sensible comparison would be a black or Asian person saying to a fellow black or Asian “look how dark you are I would hate that”
And trust me, comments like that are unfortunately said within the black and Asian community a lot! It’s not racism but it’s called colorism. Especially common with the older generations. The Indian caste system is even linked to colorism.
And colorism is much more deep than squealing against the colour of someone’s leg, it’s a prejudice against darker tones that can affect promotions, gaining employment, prison sentences, likelihood of getting married, being an actor, music artist etc hence skin bleaching is common in certain communities.
OP, this doesn’t sound like a friend. She’s negging you and might be jealous. I’d keep my distance.