If you do confront her about your suspicions, does she stay silent? Does she divert or distract or gaslight? Not only is that a sign of infidelity, but it’s a sign of abuse. If the relationship is important to you, you should work on this tactic together; if neither of you are capable of that, you should get out.
6. Hiding Her Phone
This is pretty standard cheating behavior. Is there suddenly a passcode on her phone when there wasn’t one before? Does she never leave the thing unattended with you? Is it because you’ve invaded her privacy in the past or is this a completely new and unwarranted thing? Maybe ask! Hey, I’ve noticed that you are suddenly being protective of your phone and it’s making me feel suspicious, is there something we need to talk about?