Went through her phone last night 25f and 28f Do I tell her what I found?

A Reddit user recounted their emotional distress after looking through their partner’s phone and finding upsetting texts and potential unfaithfulness. The user admitted they had never done such a thing before.
Found their partner mocking heartfelt texts, laughing at insults about their appearance, and flirting with an ex. Now, they’re unsure whether to confront their partner or how to proceed. Read the original story below:
‘ Went through her phone last night 25f and 28f Do I tell her what I found?’
I’m (25f) at my job today, still rattled by what happened last night. I went through my girlfriend’s phone while she was sleeping. (28f). I’m unsure of what my next steps should be. I had a lot of faith in her and only minor suspicions. I’ve been deceived before in a relationship and regretted trusting without question, so last night I looked through my partner’s phone for the first time.
I’ll list the things that I saw, in order: – Her best friend and her making fun of a heartfelt text i sent when we were having issues, calling me a b**ch
– That same best friend making fun of my appearance, and her laughing
A picture showing her engaging in flirtatious exchanges with this guy on Instagram and requesting that he purchase a plane ticket for her to visit him (I looked at Instagram and saw flirting that started around the time we began our relationship; they had been romantically involved before)(it’s possible she was joking, but he also reacted to suggestive pictures she posted to her close friends with likes and called her attractive).
I had a panic attack last night and didn’t get any sleep. I will be reading and responding to every reply, I don’t know how to deal with this. Do I tell her what I saw?
Here’s what the community had to contribute:
giag27 − Why are you even with this person? It looks pretty clear to me what her intentions and her true feelings are. I’m sorry Op, confront or not, you should be out. Good luck.
CanuckGinger − Just tell her it’s not working for you, end it and walk away. Don’t waste your time on confessing the snooping. She’s clearly a POS.
Upbeat_Money18 − Why bother with the argument. Just leave, go no contact and move on with your life. You don’t owe her an explanation or the energy of a fight, because 100% you’ll be gaslit into it being your fault for looking.
LEARN AND UNDERSTAND YOUR VALUE! You merit companions and significant others whom you can have confidence in and who will stand up for you even when you are not present, not individuals who exacerbate situations, find it amusing or use derogatory language towards you. Her actions have revealed her true character, so accept it!
vaydevay − Even if she wasn’t cheating, she sounds really mean.
m0nst8r − She’s not the one for you
cp1390 − She doesn’t act like she respects you. Especially talking smack about you with her friend
Appropriate_Power116 − When one feels the need to start going through phones, the relationship is already over
Direct_Commission492 − Why would you give this person any more of your time? You saw clearly what they feel for/about you. You saw it with your own eyes in their own words. Time to shut that door and move on.
Reinefemme − i’d go full ghost honestly. this is egregious and there’s no way up. she doesn’t respect you. she’s actively cheating.. why do you want to stay?
20150711 − RUN
Is it wiser for the Redditor to discuss their discovery with their partner directly, or would it be more effective to tackle the fundamental problems within their relationship? What would be your course of action upon uncovering this kind of information about a person you hold dear? Please share your perspectives and guidance in the comments.