May or may not be an important tip, depending on what her parents are like, how old she is, etc., but make sure she realises they switch ends at half time.
My mum told me about er first football match, where she and her sister went to watch the game, came home and to check they went my granddad asked them the score. They said 4-0. He thought they lied about going because they didn't realise the teams switched ends at half time, the match was 2-2.
I took my girlfreind and her boy to stockport sat , girlfreind enjoyed it for some silly reason but her son was not impressed a two year old arsenal fan currently.
I took my current partner to her one and only football match to see York v Brighton in 198something. She has never shown the slightest desire to see another game of football. She is still with me, bless her, but slightly concerned about the amount of space my programmes and other football memorabilia take up.
I took Mrs Gloves to the old Den for the second leg of the play off semi in 91. She said the burgers looked like pedigree chum and was slightly concerned when some of the Millwall faithfull started chucking seats and set light to a Metropolitan Police helmet (said officer was not wearing it at the time!)