If my partner trusts me with their phone does that prove she's not cheating?

I've only been in one another relationship my entire life and my partner ended up cheating on me, which caused me to have trust issues. Then I found out my brother cheated on his girlfriend and his girlfriend cheated on him, so now I have a really hard time trusting anybody. But my current partner lasts me use her phone, like we'll watch videos on her phone, she doesn't hide any texts from me (I can see her phone, but I don't read them I just noticed that she doesn't try to hide it) and she lets me hold her phone when I need to write something down that's on her phone. So I keep telling myself that the fact she trusts me enough to hold her phone and when there's a text notification she doesn't hide it that proves she isn't seeing anybody else behind my back, right? I do trust her, she's never lied to me a single time. I used to have doubts, but I would always get proved wrong and find out she was actually telling thr truth.
If my partner trusts me with their phone does that prove she's not cheating?
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