I'm afraid I can't tell from your last reply whether you are or aren't expecting to have access to her phone or whether you have previously accessed it without permission. Could you rephrase?
Everyone is an individual. Just because one person is OK with something that doesn't mean another person will be too. She is not her husband, so it doesn't matter what he allows you to do with his phone. Similarly, your trust issues do not oblige her to agree to anything she doesn't choose to agree to. You will find yourself much less frustrated if you stop expecting that it does.