<human>: Last week my husband was on a business trip, and I had to work late. I mentioned to my neighbor, Nick, that I was looking for a babysitter for my son Cooper, and wondered if he knew anyone. 

Nick told me that his 16 year old daughter, Emma, was hoping to get started babysitting this year, and would be happy to take care of my son for a few hours for free.

Before going to work yesterday, I thanked her for agreeing to watch Cooper after school for the few hours before I came home. She said "Really, you should thank my dad... He made me do this." I was a little uncomfortable with this, knowing she didn't want to be doing it, but I had no time to make other plans. 

When work ended, I got on the highway to drive home, and there was a traffic jam that held me up for over an hour. I called my house to apologise to Emma about how I'd be back late, and she said "Ok, but try and hurry.. I have homework I haven't started tonight." 

When I got home Cooper was very hyper. He mentioned to me that Emma had made them chocolate banana milkshakes, but he didn't like his too much because it was weird and bitter tasting. I thought that was strange, because neither of those ingredients should be bitter. 

This morning, after having a lot of trouble getting Cooper to sleep the night before, I realized what might have happened... I gave Cooper a small sip of my coffee, and asked him whether Emma's milkshake had tasted like that... He said "Kinda... But I'm not sure, it was just gross." 

I can't be sure she gave him coffee, should I say anything to Emma's father? From the way she seemed annoyed with having to babysit, I definately suspect it...

Provide a brief overview of the text.
<bot>: Neighbor's daughter babysat my son and may have given him coffee at night, annoyed that I got stuck in traffic and came home late. Should I confront her father, or her?