Remote Assistance - 'host name could not be resolved'

I'm trying to assist my mom remotely using the Remote Assistance feature -- I get the error: REMOTE ASSISTANCE CONNECTION COULD NOT BE ESTABLISHED BECAUSE THE REMOTE HOST NAME COULD NOT BE RESOLVED.

 

I've read the previous threads -- have had her turn off her Firewall, and we both have DSL lines, so there shouldn't be a problem with the internet connection --  have tried several times to connect. 

 

I read about opening the ports on the routers, but don't really understand how to do this?

 

Any suggestions?