Oooohhh this is a good one to think about...
For the first part... I think Mia would be one of the first tbh. I mean, she always complains about the serving size in Japan, so she'll constantly get bigger and bigger plates, so she's on the fast track for health issues I feel.

As for who would have it the worst... It's my usual suspect Yoshiko lol. I think other than her atrocious luck guaranteeing an early heart attack... I believe she would be extra delusional about her issues and actively refuse any medical assistance I feel, making it worse for her

Like her pounding/erratic heartbeat is a sign of her fallen angel powers growing, her gastrointestinal issues she passes off as her mortal form struggling with all the mana she's receiving, her sleep apnea she believes to be the work of God's angels trying to get her, etc.