Ensure you tell her you are going to meet pops before you do it, explain your reasoning why. If she does not agree, respect her wishes, if you disagree --- find a new GF.
If you do it behind her back and she really feels strongly against her dad, you will be finding a new GF because you did not build trust. Talking to her mom about things that do not affect you but affect her in a significant manner can lead to bad things.
Sounds like Nick wants some older -<
