Jesus Dude, start small!
She ever use one before?
I actually just finished fucking my wife with her black dildo lover.
I also started large and she couldn't take them until after a kid.
She also said she'd never use a vibrator or dildo, after the first time using the vibrator, she fell in love. Dildos took awhile longer and I found out why, took me awhile, but I figured it out.
My wife is all about the touching, I find she cums the longest and hardest when I have more contact with her while trying to insert a dildo.
A month ago I bought a BBC dildo with the suction cup base. The first time we used it, I set it up behind her so she could fuck it while I moved around to her front to kiss, talk dirty and and suck her tits. She went fucking crazy and I mean crazy! Afterward she said it felt incredible being pleasured from both ends, she said it felt like two people were pleasuring her.
Same thing this past weekend, Friday night she came twice with it in just a few minutes and then again tonight. After her black dildo lover fucks her, I get to. All I can say is that that fat pussy is loose and wet. She then makes me cum as she talks about how good another dick felt in her.
Small steps I guess, hopefully some day it will be with a real BBC.