You could validate her feelings...

for example

really listen to what she is saying

w: someguy...I don't love you in that way and you deserve so much more than just someone like me who thnks of you as a friend

someguy: you are right w...we all want someone to feel that special love for us

w: see someguy??? I just don't feel that for you!!!

someguy: wow wife...that must be really stressful for you to have to feel like you have to fake those feelings for me all the time. I hate that you have to feel that way.

you want to let your wife know that you care very much ABOUT HER FEELINGS...this isn't all about you

you want her to know that and by constantly reminding her of how you feel, all it does is make her feel guilty

she can't feel safe with you when you are making her feel guilty and feel pressure

what would you say to a friend who said they didn't feel that spark for their spouse anymore???