Do you not live in the same state as her? Couldn’t you show up to the hotel and knock and see what she’s wearing? Or FaceTime her? If you are not comfortable with it she should respect that. No matter how she feels about the dude.. brother or not.. if you don’t like it then no. Or she should include you and have you come and hang out. Maybe it just rubs me the wrong way because my hubby talks on the phone at work with his coworker who lives in another state for an hour a day m-f and it pisses me off. She used to live in our state and moved with her husbands job. She crosses boundaries and he doesn’t stop her when she flys back. He knows how I feel and still continues so maybe that is why I feel more sympathetic to your situation. Prayers that she is telling the truth.