ask her about herself
now, don't get all creepy by interrogating her! The answers are not all that important so don't badger her for them. It is like playing with a balloon, you just want to keep it (the conversation) up in the air so you bounce it gently
ask her how her morning was (before she got in the car)
ask her if the excitement of the trip disturbed her rest the night before
Ask her what her favorite game was on long car rides when she was a kid. Take your cue from what she answers with ( out of state license plates, 100 bottles of beer on the wall, what ever and when the conversation lags call out an out of state license plate, or start with 15 bottles of beer on the wall. You don't have to play the game, just let her know you are passing the time with her. Being a companion is all that matters.
So when ever the conversation lags ask her more about herself. Be prepared, she might ask you about yourself, too. And that is good
and laugh when she says something funny. Be happy, be lighthearted, show a sunny side, (but don't be manic about it,) just be solidly contented that you are with her, and getting to know her. That will set the mood.
Together, you two can face any adventure that comes your way! Have fun!
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Alis volat propriis
State Motto of Oregon