Do you think it is okay for me to lie to my girlfriend?
Is there a reason behind it?
Yes, my girlfriend is pressuring me to tell the truth.
You shouldn't just lie because someone told to tell the truth. Maybe you will learn something about telling the truth.
I don't want to talk about it.
If it is a little white lie that does more good than harm, then it might be necessary to do so. You seem like you want to protect your girlfriend from the harsh reality, so in this case, you should weigh the pros and cons of the lie.