My girlfriend cheated on me almost our whole 2 year relationship and acts like she did nothing and is living her life normal why?

So a little background

She cheated on me with her ex the entire relationship I found out almost 3 weeks ago and she's been trying to get me back, she's been always asking to go out and do things but she gets angry when I shut her down and goes completely dry and acts like she didn't cheat on me, she would block me then unblock like you arent the one that cheated? even tries to justify it in a way

There would be constant arguments back and forth she would tell me how she doesn't see me the same, told me if I really loved her I wouldve reassured her because she claimed she was only with him because of a trauma bond but from texts she would invite him over, she has got mad at me for not wanting to do things and everytime I tell her I'm hurt and the reasoning why and she acts condescending and sends gifs like she doesnt care at all.

It's embarassing I was trying to work things out because I genuinely felt like I couldnt live without her, but she lives her everyday life like she did nothing and her friends don't think shes wrong, she's been going to parties, going out a lot, always laughing making jokes and everyone wants to be around her, It's sad I still look at her stuff and see these things and it's just she doesn't care at all?

I blocked her yesterday completely I was telling her how I felt and she just kept replying with " Nice " then went out to a party, she feels like she's been trying her hardest to get me back which was just asking me to go out all the time, and her crying because she told me she felt lonely and she missed me and loved me its a lie completely and Im just hurt and I dont wanna look at her stuff anymore.

if you guys wanna know the full backstory on how she cheated Ill make another post but its okay if u dont

TLDR; girlfriend cheated and acts like she didnt and lives her day to day live normally