Salam,

Just show her the benefits of Hijab, Inshallah she will see them sometime. But you should not brake up with your friends only if they are taking you away from your faith.

Assalmualykum,

Very good advice from Hadhrat Ali ibn Abi Talib

"A friend can not be considered a friend until he is tested in three occasions:

1. In the time of need
2. Behind your back
3. And after your death.

[Hadhrat Ali ibn Abi Talib ]

Salam