It's a fine line, singularity, between you wanting to control her and her wanting to keep her options open. Only trust over time can help you distinguish where the one thing ends and the other begins. I agree with shh!. Her past is none of your business unless she invites you to it. Her friends are for her to deal with, not for you to manage. Whether she does the right thing with friends who may make overtures to her is for her to respond to, not for you to command. I sense you're a little more insecure in the relationship than might be good. Extend her the benefit of doubt. She might well put your concerns to rest without any prompting from you at all. I'd think you'd, at least, want to give her the opportunity to.

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Speak less. Say more.