Instead, she is offering to bring the dog over for a visit.
Why would you say no? Are you worried you'll have an R talk? Are you worried you can't show your W your good side?
Make plans to go out AFTER the visit. Be dressed to the nines and have a plan to go somewhere (make sure you have a plan to go somewhere). That way, if you start to become uncomfortable, you can make your exit with the valid excuse that you are going somewhere.
It doesn't mean you hang with your W all evening either, if things are going well. Let her enjoy your company and then excuse yourself. She will have a GOOD memory of you to miss.