My brother got cheated on and is in denial

My brother lives with me and rents my spare room along with his girlfriend who is a bit of a character, she has given us many reasons to be suspicious of her the past 8 months especially up until a week ago when we got a confession from our 2nd brother that is a twin to my brother, that he had sex with her. She denies it at every angle but the holes in her stories and the red flags really are making it hard for me, my husband or any of our friends to believe her. So for a few weeks back in November and December our other brother was coming down to visit (3 hour drive) and staying on our couch for 4 days and 3 nights, every night me and my husband and my brother would go to sleep while this girl stays up on the couch all night with the other brother. She would follow him around everywhere and every time he went to go have a cigarette shed be outside with him, which she normally never does with her bf. She even locked me and my husband out of our own house trying to rush me out the door when i was taking things to my car. Then she proceeded to tell the other brother if she wasn’t with my brother she would be with him! Hello red flag. She also has been caught sending naughty photos to some guy on Snapchat and clearing and hiding the conversations. She is constantly looking at other men when we go out saying “ooh hes cute” and trying to talk to these guys. So now when the other brother confessed they had sex he said it was on a specific date that i recall and even have ring doorbell video evidence of, they said they were gonna go get something from the storage unit at 9am they left, 3 hours later i text them and go “where you at” and they say they had to stop at grandpas house to get something and they will be back soon, then at 3 i get a text asking if i want mcdonalds and i decline and they dont return until 4pm, and well if i can count thats 7 damn hours now who takes 7 hours to run 2 errands and hit mcdonalds? I feel like im losing it presenting all of this evidence to my brother and he just wants to believe her but ive had this gut feeling for a while that something is going on and i swear to god this woman is not good for him i mean the last time she got confronted for being a whore on snapchat she packed all her **** called her parents and ******* left then came back and cried and begged to move back in, in the same ******* day. I do not like this woman and im kicking her out of my house but im afraid my brother will follow her and get even more hurt. Does anyone have any suggestions or agree with me that she more than likely cheated? Thank yall for reading, have a wonderful day/night!