this message may be offensive
your friend treating you like shit and backing it up saying "you're strong you can handle it" is just a sorry excuse to continue to treat you like shit.
If you don't like it, if it hurts you in anyway, speak up. tell her to stop. that girl is not your friend. the second you speak up, she'll worked up, blame it on you. you shouldn't let that happen. slowly slip away. if she cares enough to ask, don't fall for it, she really doesn't, she just wants a punching bag.