Is it wrong of me?

My 2nd cousin turned 17 yesterday and her mom is having a “little” get together for family for her birthday this Wed at 5:30. I work till 3 and have SO MUCH college work, so I texted her saying I couldn’t make it due to all this, but I wanted to drop her present off today. I feel like it’s wrong of me to not go.. but it’s a weekday and it’s I’m so busy! What should I do?