I want to ask my new girlfriend to delete her dating apps
How does it make you feel knowing she still has those apps on her phone?
I feel like it's not good for her.
It sounds like you just want to have loyalty in the relationship. If she is your girlfriend now then why would she still keep her dating app? It sounds like if you don't make her delete the app, the chances that she will cheat on you would be very high due to temptations.
I'm not the most handsome guy she has ever dated.
I don't think there is anything wrong with wanting loyalty in a relationship. You can communicate to her how those apps make you feel now that you are in a relationship. If she cares about you enough she will take them off.