It’s still not working I restarted my phone and watch hers as well still she can receive the invite to add me on the walk-in talkie app

You both need to set up the FaceTime app on your iPhone with iOS 12.4 or later and be able to make and receive FaceTime audio calls. 

The Walkie-Talkie app isn't available in all countries or regions. 

Apart from checking again the article that you came to the community from  

Use Walkie-Talkie on your Apple Watch - Apple Support

you could check that you have no security apps or VPN that may interfere with the handshake.

Force restarting both watches and phones may help.

Its a bit of a pain unpairing the watches from the phones and setting up again but that is the final remedy.

If you've completed all that troubleshooting and the issue is still not resolved, use the link in the article to Contact Support. 

Click here > Contact - Official Apple Support  

or phone numbers  

Click here > https://support.apple.com/en-us/HT201232