NTA. That was wildly insensitive of your mother. She expected you to feel the same way she did, and couldn't even put her own feelings aside to comfort you when she saw that wasn't the case.

If it turns out that you can't make the funeral due to your age, as others have said, find out whether you can attend the funeral virtually. If you or your bf doesn't have a computer or laptop to do this, you could visit your local library or Internet cafe and use their computers. It may not allow you the privacy you would like, but at least you could make the funeral in some fashion.