Jealousy?

My partner recently told me about a girl that’s been flirting with him and won’t accept the fact that he’s taken. He told me that there’s nothing to worry about and I believed him for a while. Recently he gave me his password and let me log into his snap without me asking. She snapped him and it was clearly flirtatious and his replies seemed a bit flirtatious but that’s just his personality and I completely trust him. The only thing is my friends who are also friends with the girl have told me so many stories about her sending nudes and such to people who are taken and told me I shouldn’t trust her. I’m kind of worried that somehow she’ll manage to snake my mans? What should I do?!?

Edit: she admitted that she’s in love with him and talked about how depressed it’s making her. I feel bad, help.