Was this really that bad?

I've been with my girlfriend for 2 years and it was her moms birthday (me and her mom don't get along) and the entire family was going to be over, about 30 family members. Her mom is 65 years old and married. Well as a b-day gift I gave her a huge vibrator, a whip, and some adult DVDs. The old hag was very ingrateful. She began yelling and trying to get the family to hide their eyes or walk away. It was a harmless prank and she didn't think it was funny. Was this so bad?