If you're 19 does she want you to call her Mom?
Do you love HER? THAT is the question. You should never make arrangements to live with someone unless you really love them. The age discrepancy can be overcome if you REALLY love her...but at this point...you are asking US....so it sounds like you are unsure....about everything.....how you feel about her....the age difference....her moving in....if you loved her, you wouldn't be on EP asking our opinion....you would have gotten yourself a truck and moved her things into your house and counted yourself lucky.
You really looove her...you want to maaarry her....YAY!!!!! GET THE TRUCK!!!!! HUGS!!!!! Thanks for best answer!!!!
Tell her welcome aboard the love ship.