I feel really horrible and even suicidal

Dude, come on... it's just woman, there's literally billions... and most aren't this terrible.

Nothing make sense

That's because you have a small sample size of women: your mom - who you probably idealized and hungered for her affection and a narcisist that fed off your hunger for affection. As you get to know more women, the first will seem silly and the second will seem like obvious bad choices.

she pretended to like all the things I was into now she hates them and likes all the things her new guy is into

Women don't like anything, they don't have hobbies, they are but a reflection of the men they are with.

When I finally found out and confronted her

Why? whats the purpose? she's already gone for ever. She don't exist anymore, there is nothing to discuss. Just vanish like if she never existed because she don't, no matter if she loved you last week, now you are nothing for her. That's how women's mind work.

Now they are posting happy on social media together which makes me more confused

Poor unsuspecting guy, she will do exactly to him what she did to you, mark my words. People don't change.

Classic narcissistic gaslighting. Be glad she's out of your life. Block, delete, change your number, change email, etc. Don't look back, there's only smashed windows and slashed tires waiting for you when her new narcissistic supply runs out.

" I feel really horrible and even suicidal."

My dude, you should feel relieved that you dodged a bullet, and now the same shit she pulled on you is the next guy's problem. It could have been much worse, so count your blessings.

Women be shopping. Take the pain/anger/bitterness and use it. Use it at the gym, at school, at work—use it. You dodged a bullet. Remember the pain moving forward - don’t get too invested

Nothing make sense

Sadly you've dated a girl who is mildly BPD / Psychotic / Liar. They're not all this bad, but many are.

Mistakes you made:

When I finally found out and confronted her - she had a tantrum blaming me.

You had a discussion with her. This was the mistake. This was actually weak because you wanted her to apologise, or you wanted her to be sorry, or you wanted her back. This is a weakness in you.

The strong move is to eject her from your life, delete her everywhere, and never look back.

You're not there yet and that's fine, but I'm telling you how to handle it next time.

Yeah - just make sure you save some screenshots etc and any contact you have. You might even have a case right now for harassment against you. Feed them the bullshit they're trying to pin on you.