She believes it.

You watch as Shari sets the box on her bed and opens it. She takes out the portal that has your genitals, then mutters, "Sure does look real." She tosses it on the bed, which gives you a small rush as your penis hits her sheets.

She takes off her robe, exposing her D-cup breasts. You feel your cock growing in response to the sight of your neighbor in all her glory. Shari notices, but just shrugs, seeming to chalk it up to the "realism" you mentioned. She climbs on to her bed, grabs the"dildo" and spreads her legs. She rubs her finger in her snatch a little to get her juices flowing, then unceremoniously shoves your penis into her and starts pumping. You feel odd watching her as if it's a porn video when you have all the sensations of your dick moving in and out of her pussy, as well as your balls repeatedly slapping her butt. Eventually you realize it's like the best of both worlds, as you have an amazing view of her vagina taking in your member. Eventually, neither of you can take anymore and you both orgasm, her moans sending shivers up your spine.

"That DID feel real," you hear her mutter. "I could almost swear I felt that thing cum in me."