There isn't enough information here to go on but why do you think she's ashamed of you? Could her background be the reason?
I don't want to say she's cheating on you without proof so you need to ask her when she visits why she doesn't want you visiting.
You could land up in the area and call her to meet you near her school saying you missed her. You might not meet her friends right away but she might get used to ur presence and slowly get introduced.
Good luck.
There ase many explainable reason, but u sud try 2 ask ha first!