She is scared of upsetting your relationship, so you need to be clear what you are asking her to do. Has she got some condoms in her purse? Do you lick her wet slit as she is reading the texts to you from her phone? If she gets preggie to one of these new guys, what will you do? What are your true feelings for her?
True love can be all about her getting fantastic sex with a number of guys with your encouragement, but are you ready to stick by her "for better or for worse" ?
Remember than you are wishing to share her with other guys, and her body may want this extra cock-power to be a regular thing during your marriage to her. No room for changing your mind later on if you get pangs of jealousy when you see her open her legs for guys with cocks much bigger than yours.