How can i start conversation with this girl in my grade... we both have eating disorders?

we are in 9th grade, the same Homeroom. shes good friends with my acquintance i guess u could say (who told me a little about her eating disorder, but everyone kinda knows.) she is 85 pounds and about 5'1" and i'm 84-86 pounds at 4'11.5, so we're close in size. i want to be friends with her, but how do i do it without being awkward.... what could i say to her?