My little sister (14) no longer wants to be muslim because she is tired of all the rules such as modest clothes and no relationships and doesn’t like our culture. She wants to be able to have her own freedom to live her life without parents telling her what to do. We don’t know how we can bring her closer to Allah. She doesn’t care nor put in any effort to try

I recommend you show her the beauty of Islam. She probably doesn’t see the beauty of it. I recommend you have her see these videos, or you see them and share with her their main points: