I am very sorry for the pain you're going through right now.

Consciously repressing your sexuality seems really difficult and exhausting, and has got to hurt. Unconsciously repressing it is something that other people do, and it also hurts, although with less awareness.

I think it's so brave and admirable that you have clearly decided for yourself that if your mom told you to live your life as if you were straight, you "wouldn’t get married with a man because simply I don’t want to and there is nothing will force me to do it."

Keep in mind that there's going to be some difference across the board in the way people deal with homophobia from their families depending on the time period that the person lives. OP's girlfriend probably was 16 at a time when society's messages about being gay were different than they are today.

But ultimately, everyone is different. Some people repress their sexuality as well as their own awareness of their sexuality. Others might repress and hide their sexuality from others but not from themselves. I don't know all of the things that go into why someone might end up being closeted from themselves and everyone else, and why a different person might end up just closeted from everyone else, and why another different person might not be closeted at all.

But seriously, kudos to you for your bravery and strength in the face of homophobia coming from your own family. It's no small thing to face hatred of who are are from the people that should love you unconditionally, and it makes total sense why you would choose not to tell them given the messages they've sent to you predicting how they would react. Even having made up your mind that you wouldn't marry a man if your mom told you that you had to is a really great, admirable thing that I think you should be proud of, even if you have to keep that pride all to yourself for now. :)