Stay friends or drop em

I’m having a few issues with my long term best friend().we've been together Scene 5 grade and have been insertable.We've help each other through dark times and accept each other for who we are.Were both 13 and have been going through very big body changes (me mostly in the chest and her in her lower body)many have told me I’m evenly portioned and that I have a pear shape even though I’m very skinny and tall.Around a year ago she started to develop more in her lower region and I never really paid attention to it because I’m mainly confident in my body and don’t have a problem showing it off or wanting to make my self look different.My best friend on the other hand I know has many insecurities but I’m not quite sure if she has them in her body.Last year she started to tease me about my butt being small even though hers is relatively to it just more noticeable in her clothing than mine is in my clothing.I didn’t really take notice to it and pushed it to the side and laughed it off.It still kinda hurt me though considering this came from someone I would Least expected it to.Before it wasn’t a problem but later a couple of months she made it a point to bring it up whenever she could find a chance to like how at her birthday party she had her other friend over for a sleep over and she is relatively well built in her lower region as well.They both started to tell me I have no ass and that theirs barley anything there which made me fell kinda bad about myself but whenever I look in the mirror all the hurt goes away cause I see the beauty I really have.They both had a melccous tone in their voice like they were trying to hurt me intentionally and started laughing.Then on another occasion when I was laying down on the bed she came over and started to say look at me showing of my checks and then proceeded to say their a little plump in a snobby tone.when I tried picking her up one time and got almost dropped I said that she was heavy in a joking manner she proceed to say your just mad cause I’m thicker than you and rolled her eyes.The only reason I really have a problem with it is because she’s just brings it up out of nowhere to be spiteful.I get that I’m usually the skinny only out of the group even though people tell me I’m kinda thick and have ass it just makes me wonder if she’s insecure because her and my cuz who just recently moved in with me make it a point to tell me I have no ass even though my cuz tells me I’m evened out and I can wear body fitting clothes unlike her cause she’s plus size. They always put me in the middle of the bed cause I’m the “skinny one”.when I was chilling in my underwear they told me to put some pants on because my long skinny legs disturbed them.Me and my cuz we’re recently talking about cup size and how I can’t fit a a or b anymore and that I need to get rid of those bras because my chest pops out every time. I noticed that my best friend got quite and started to indulged into her phone because I’m not gonna lie she’s a very small a cup.Recently when she was over she would flick or poke my butt for no reason if I was laying down or standing up and I don’t know why.I know I mite sound whinny and super sensitive for taking this personal but it hurts me at the fact they are criticizing me for something I can’t really help or control.I’m only 13 and it feels like they expect me to have the body of a grown women and to be perfect even though I’m not.I know this is really long and I’m sorry but I just really need advice on if I need new friends or to work things out.it’s a new year and I really want it to be not filled with body shaming and making me feel like I’m not able to stand up for my self.Pls help