Sextones...I think the best way to find out is to really listen carefully when she tells...what you should try to figure out...does she return your fantasy...as you expressed it..?
I have experience enough in this matter to know one thing...fantasy and reality is quite different...mostly because...in your fantasy...your wife is casted by your lust...all she does up there...in your head while your jerking off...is a product of your fantasy...just remember...she is not...
When she indulge in your game...she is going to do it her way...maybe trying to do all you want...but still...there will be some things you would not expect should happen...(maybe you will like it...maybe not)...
And then there are the third party...the man...and here is often the most "difficult" part...because he has never been involved in your talks/begging/fantasy...and he is not a human dildo...he is a permister...with his own opinions and will...
E.g.
1) you want him to humiliate you...he has no interest...he just want to fuck your wife...
2) you want to suck his cock...and tell him...he is definitely not interested...call you a weirdo...and leave
3) you want to watch...he don't (men are normally kind of secretive about such things...)
4) you want him to fuck her bareback...he don't want...
5) you want him to fuck her whenever possible...he can't (he has a life you know)
6) you want to clean your lady after he has left his juice in her...he get to know...call you a fucking weirdo...and never comes back...
7) you want him to be dominant with your wife...it turns out he is submissive...he just wants to have sex...with your wife...
8) you want him to fuck her silly with his large bat of a cock...turned out he didn't have one...just a small toothpick...
9)you want him to fuck her hard and long...turns out he cums fast...every time...
Your fantasy may have all kind of nice and/or perverted perceptions of how he will act...but mind you...it's not like buying a car...you are not in position to write a specification...and purchase accordingly...
Sorry if I put some bumps in your road...but this is the real thing...
My point here is....if what she tells you is what you have told her...she is just teasing...
Why don't you put out a little trap..? Tell her that what your fantasy tells you theses days is xxxx (some realistic but special cuckolds brownie)...and see if she responds to that...one day she tells you:
"and my love...you know what he did to me...he xxxx'ed me...can you believe that..?"
On the other hand...why would you like to do that..? Maybe she is just telling you little white lies...to keep you happy...and if you disclose this...and confront her...well, maybe she will stop...and defiantly never indulge in your fantasy again....
Up to you....
A cuck to my GF - A bull to all other women