Girls only: Should I go or not?

My friend I haven't seen for like 2 years invited me over to her house for a sleepover and I got my period a few hours ago, and I can't take the cramp reliever pills because I'm out and I can't take the advil because my mother needs it for her headaches too, and I know if I go and try to endure the pain I'll just end up being miserable because sometimes my cramps get REALLY painful I know I can take one before I leave but I usually get cramps up until the third or fourth day of my cycle. What should I do? She's busy for the next 2 weeks because she'll have summer camp.