When my wife went through breast cancer, I will never forget when the surgeon came out and told me the lymph nodes were clear. I had been pretty rock steady throughout neoadjuvant chemotherapy and all that entails as a supportive spouse, but when I got that news, I felt like I needed to be mopped off the floor. Because that really is the big question.
Just a bit of advice, as part of the reconstruction process, she'll have drains. They tell you in the hospital to keep them clean, etc. But in the US, at least 10 years ago, they tend to leave the drains in for a while (and you get sent home with them). What they should tell you is you need to keep a sterile field around those things at all times. Reconstruction was a lengthy process with multiple infections, but we eventually got it done.
Working in your favor is that she didn't opt for immediate reconstruction, i.e., spacers immediately following the mastectomy, and she hadn't undergone chemo prior to surgery, which means her immune system is in much better shape than my wife's was. But don't sleep on those drains. You cannot have enough rubbing alcohol in residence based on our experience. Stock up. And all the best to you guys.