Girlfriend freaked out when I touched her phone?

We've been together for almost a year. We're both 24. Last night, we had a bonfire on the beach and I left my phone in my pickup so I reached over to her phone to see what time it was. She freaked out! I've never seen her move so fast.. she literally snatched it out of my hands. I've NEVER snooped through her stuff because I've always trusted her. That whole incident pissed me off and has made me question our relationship. I've been 100% open with her from day one. In fact, she's gone through my phone dozens of times. What does she have to hide? I'm seriously considering breaking up with her.. I feel like she might be playing me.
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I think it's too late to ask her about it. IF she was hiding something, she's probably already deleted it by now. I've never seen someones girlfriend or wife ever act that way, I guess that's what set off the alarms.
Girlfriend freaked out when I touched her phone?
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