Hi, the fact that she’s interested and aroused by the idea during pillow talk is very encouraging. This indicates she enjoys the concept, but is likely reluctant to have confidence in the reality of it being possible.
You’ll want to find out what her reservations are and address them directly.
For some women it’s doubt that other men will find them attractive, for others it’s an assumption that you’d only offer such a thing so you have justification to have another woman (very common misconception).
Download my PDF guide on the marital role of hotwife and share it with her – let her see that this is actually done by many couple and that it has a name and that you share this desire with many other couples. Then you can bring her to my main site, http://cuckoldmarriage.info and begin learning more together.