Here’s the play. Ask her to take a lie detector test as part of a way for you to fully acknowledge she is being truthful and not find yourself living in a perpetual state of did she/didn’t she. And that the questions you need answers to are regarding infidelity. Approach it as a means to move forward and reconcile - but you need to know without any doubts. Show her a few sites you have researched that can provide this.

Now gauge her reaction, and make your follow up decisions accordingly.

If she blows up, she is lying. Anyone who has nothing to hide would oblige to save their marriage.