Sadly, keeping it a secret is very common, oftentimes because there is so much shame attached to it. As you said, it's an honour that she opened up to you. You're doing great by seeking out some advice. You might find this helpful as well.

I know that if I were in this situation I would consider counseling.

Try not to make assumptions about you would do. The truth is that until you've gone through something like this, you don't know what you would do. Going through a traumatic experience like this generates all sorts of reactions/coping mechanisms which might look odd from the outside, but which are what the survivor needs at that time.

Should I seek out a counselor for her, even if she doesn't want to try it?

Absolutely not. She is a competent adult capable of making her own life decisions. She doesn't need you to rescue her - she needs you to respect, support and love her.

Just because you don't understand her decision doesn't mean it's wrong. Going to therapy is a huge undertaking and would likely affect her entire life - work, home, etc - not just the hour a week that she's actually in the therapy room. It's a serious decision and commitment to relive past pain. Therapy must be her decision only.

At the same time, just hearing that someone you love has gone through a traumatic experience can be traumatizing for you as well. It sounds like you could benefit from your own therapy to help work through these emotions... something to think about.

Should I treat her the same as I always have or should I do things differently?

Take your cues from her. Gently but directly ask her if there's anything you'd like her to do differently, or any way that you can help her. If she says no, then respect that and continue to treat her the way you always have. After all, she's been a survivor for the entire time that you've known her.

It makes a lot of sense that you're struggling with your wife's revelation. Hang in there, you will work through it together.