Shall I Ask her about the affair...

[dwh15]

You didn't give a lot of history but if she left to get some "space" and now is coming back into the marital home, I would definitely want to find out details of the affair and whether she was still in contact.

Letting her come home with no consequences is sending her a message that she can get away with this kind of behavior whenever she wants. Does she seem remorseful at all? If she's not crying and begging you for forgiveness, promising to do anything it takes to save your M, then I would be highly suspect.

It's likely that the A is still ongoing or that she will have another one in the near future. You need to get honest details and put a stop to this now. Take it from a guy who let his WW pull these stunts for nearly 5 years. In the end I find out she has been with 4 OM and left me for the most recent one. You don't want to end up like me. Make your W earn her way back.