sister is stealing from me?

my sister has been known to steal and this weekend she came over to my moms house where i also live but i wasn’t there that weekend and i accidentally forgot my promise ring near the sink. when i came back it was gone. i’ve tried looking for it even thinking that my mom could’ve taken it but turns out my sister was here and it wasn’t the first time something went missing of mine since i’ve been here. Like 3 weeks ago a lip gloss (i know it’s just lip gloss) of mine went missing and i also wasn’t here that weekend but she was and my mom said she was in my room. i can’t ask her because ofc she’ll just say no. what do i do??