My best friend has issues...?

My best friend is totally consumed with thoughts about her weight. And she's definatly not anorexic. She eats very heLthly. She's smaller than me by two inches and she's a stone he ier than me but she still calls herself skinny! She calls me "normL" and "heLthy". she knows how much I weigh. And I'm clearly taller than her by quite a bit. And I can fit my hand around my wrist with room to spare n she can't! And my bmi is 18.2 and Hera is.... Well... I don't know, but it's higher than mine and she goes about thinking she's skinnier than me! I only get so upset be ause this is a sore subject t for me n she just calls me "normal" and calls herself "a bit too skin y". I wish I could say: " I'm lighter n skinnier than u!" but I don't wana hurt her feelings. It's not a big deal I guess, but it's annoying n hurting my self asteem coz she keeps goi g on about it! What should I do or say to her nexttime it comes up?