Should I cut this friend off?

I have a friend who a year ago slept with my man, and later tried it on with another man I was involved with. We are still friends now (she’s my roommate) but she still does the occasional sneaky thing to me, she even read my private diary the other day. I can’t tell whether she changed or not, but sometimes I really feel like blocking her with no explanation for what happened a year ago. Would it be unreasonable for me to unfriend her?
Should I cut this friend off?
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