Your girlfriend didn't consider it cheating because, in her mind, the strap on wasn't a real cock. But as her friend expertly slid the large dildo inside her, your girlfriend couldn't help but moan and squirm with pleasure. The strap-on was much bigger than you could ever be, reaching depths and hitting spots that you couldn't. And being a woman herself, her friend knew exactly how to pleasure your girlfriend, teasing and exploring every inch of her body until she was gasping for more.
As you were away for work, your girlfriend's attention and passion seemed to shift towards her girl friend. She eagerly anticipated when you would leave, knowing that her friend would give her the most intense orgasms she had ever experienced.
Unbeknownst to you, she and her friend had been fucking behind your back.
One time, when you called her while she was out of breath, she claimed to be doing a workout with her friend. In disbelief, you asked her to prove it by putting her friend on the phone. As you spoke to her friend, panting could still be heard in the background, but they both assured you that it was just a women-only exercise session. Little did you know the true nature of their "workout" together.