Seeing that Rory seems to be getting on fairly well with Paris, Madeline, and Louise, Lorelai offers to give the four girls her concert tickets, and she and Sookie will buy cheap tickets when they get there. It’s a generous offer from Lorelai, considering that she is a huge fan of The Bangles and Sookie has obtained excellent seats for them.
Some fans get upset that Lorelai gives away the concert tickets to virtual strangers without consulting Sookie (who earned them), but Sookie only got the tickets for Lorelai, and had given them to her – they were Lorelai’s tickets to do with as she wished. It would have been polite to ask Sookie first, but Lorelai is impulsive by nature, and Sookie never seems upset about the ticket situation.
It seems silly to give the tickets away because we know Madeline and Louise skip out on the concert, but Lorelai doesn’t know that’s what’s going to happen. In hindsight, it would have made more sense to just take Paris with them, but at the time, Rory thought that there was more friendship potential with Madeline and Louise.