Sister Withdrawing

I live with my sister who has battled depression since mid 20s after a miscarriage. Theres survived a few suicide attempts and self harm & hospital admissions. I'm not officially her 'carer' as such but I care a lot. Actually worried at the moment as she's withdrawn a lot, teary and not eating, not talking much, not showering and won't take calls
Not sure if I should just wait for it to pass as I think its related to an anniversary related to a major loss a few years back, but with her history it frightens me I might lose her. Its been 6yrs since her last mental health admission and I thought she was going good but this last couple weeks, its bad. Just looking for advice, thanks.