Be careful.
At first, she might be game for having another woman join the fray, but she will then demand that you return the favor and allow for a man to join in on the fun. It could get tricky. What if you are penetrating her from the front, the other man from the back and you have her sandwiched in between and then randomly find yourselves looking deeply into each other eyes (you and the other guy) while realizing that you're both "technically" inside at the same time? Thoughts which might lead you both to loosely agree that you've both been intimate in this proverbial scabbarding of swords, which can lead to you both wanting to just fuck each other on the side forgetting about the girl and possibly bringing in more men.
Look, I'm not saying it's definitely going to happen, but I have known men that end up that way.
"1"
Ménage a trois goes awry when dudes argue about switching positions, stabbing ensuesWhen Hunter asked [Orlando DeWitt, his male friend and threesome partner] to switch positions, he refused and the two men began arguing, DeWitt told police.
Hunter then reached into the couch and pulled out what DeWitt described to officers as a butcher knife 12 inches long and an inch wide.
The woman grabbed her clothing and ran into the bathroom with DeWitt, who left his clothes behind.
Hunter began pounding on the door, telling him to get out of the house, at one point forcing the door open and splintering the wood.
DeWitt told police he "decided to run for the front door," and as he did so he said he felt the knife cut his arm.
DeWitt told police he grabbed the woman's phone from the table as he ran out to call 911 from the alley.
While in the alley, he could hear Hunter yelling that he was going to kill him, and that he could get his clothing off the porch, DeWitt told investigators.
http://www.citypages.com/news/menage-a-trois-goes-awry-when-dudes-argue-about-switching-positions-stabbing-ensues-6531534