My girlfriend did something and I dont know what to think?

So, to sum it all up my g-friend and this friend from home got in touch because he was coming into town for work. They hooked up 1/12 yrs. ago but apparently have no connection and are only friends. She told me about the meeting up but she failed to mention my name to him at ALL! she made plans with him and I was to be out of town so I changed my plans and came home to go out with them. When she found out I was coming she invited friends last second from work. I dont know why she did this. also she never told him I was coming out to the dinner. WHY? Did she try to cover it all up when she found out I was coming out with them. He was not very nice or inquisitive about me and then texted her when we got home This is terrible What do you all think he meant? She had no real good reason or explanation for anything and was not even pissed at him for making me uncomfortable. I think she should have defended me. She said she did not speak to him after that and did not respond to text. T/F