I get a sense she has flirted some, but I don’t get a psychic “yes” about the cheating – an idea is to keep your eyes open, but approach her like she is faithful until you have solid proof. And be careful: if you are always in fear, expecting her to do something, etc: this can easily manifest into a self-fulfilling prophesy. You can help will it to happen with your mind, emotions, etc.
Also, who is always working on cars, or with their hands – is that you?