What if the girlfriend is too petite?

Actually, it depends on what you think. If you really like her, don't mind so much. My height is 186CM, and my girlfriend is only 155CM. I didn't dare until we were in love for more than 4 years. I told my parents that sex wouldn't affect much. The key is my parents' opinion. I had a hard time persuading my relatives and friends. If you're just worried about sex, don't worry.