<human>: We have been dating for about 7 years. We live together. Today my Dad is coming down from a different town to have lunch with myself and my brother. Like a boys lunch. 

My girlfriend is offended that: 

1) My Dad didn't invite her to come;
2) and/or that I didn't say "Sorry, I have plans with GF but she can come if you want"? 

She also states that she was just looking forward to spending the whole weekend together. It is going to be about a one hour lunch and she is visibly very upset that this is cutting into our time together. 

I love her and want to spend time together with her - so I have made it clear that we are spending this afternoon together, tonight together, all day tomorrow together and I reiterated our plans. She is still upset that is excluded. 

She states things like: 
"What am I supposed to do for lunch now?"
"If my parents came down, they would include you."

Is this just a bad case of separation anxiety? It seems like a fairly minor issue, but she is visible upset. I don't understand how she can be upset when I offered her my best for the rest of the weekend. At the same time, I don't want her to be upset like this.

Can you summarize the given text in a few sentences?
<bot>: Having lunch with my Dad and brother. Girlfriend is very upset she is excluded from the lunch. Was looking forward to spending this time with me, despite spending the entire rest of the weekend together. How can I reason with her?