Girlfriend is "hiding" our relationship?

[Elena]

Hi there! English is not my native language so sorry if I had mistake. ( in advanced)
Well when I was 20 yrs old I had bf and I also did what your gf is doing I mean not exactly but almost the same. and I feel bad evertime I remember it. there's a reason behind it and she don't want to introduce you with all her friends because she definitely hiding something and she's lying with you. My advice is confront her talk to her about how you feel and if you think her reason is good enough for you to believe why she's doing such thing then it's all up to you. but do it before you really get hurt or feel like fool and feel bad about it.