The I'm A Slave 4 U singer, 41, took to Instagram on Sunday, less than 24 hours after deactivating her account - posting an image of a birthday cake frosted with a message. "See you in hell," read the cake's lettering, accompanied by two emojis of toenails being painted red. The hitmaker's post arrived days ahead of her memoir, titled The Woman In Me. Excerpts from the book have been making headlines in recent weeks, revealing details from the singer's private life….