My sister doesn't understand my POTS

I’m looking for a friend or someone to talk to. My sister really hurt my feelings today. She told me I needed to “suck it up” at the airport and wait in line with everyone else instead of getting pre boarding to make my life a little easier. I have POTS and standing for periods of time makes me dizzy, nauseous, and sometimes makes me pass out or throw up. Pre-boarding makes my life a lot easier. She’s pretty much the only family I talk to and I love her a lot. When it comes to my POTS she makes me feel like a fake. Like I’m making everything up and that I’m lazy. When I say no to going on long walks with her she tells me to suck it up and then will say hurtful things like I wrote above. When I go on these long walks or runs with her I end up passing out and this will put me back a day or two. I end up hating myself and my body afterwards. My friends accept this fine and we find other ways to have fun. My family, their words and actions make me hate myself. I just can’t justify cutting off my twin sister.