Feeling Betrayed: My Sister Figure Invited a Stranger on Our Broadway Play Trip

So I was going to post this somewhere else, but decided here would be better... Ok, so I'm not sure how to word any of this. I guess I need an ear, maybe some advice, and a second opinion on whether or not I'm being an absolute jerk here. For context, I have PTSD from an incident that I will not go into. I don't trust people I don't know easily, if at all. I even have a hard time trusting my long term friends occasionally. Now into the story. So my sister figure and I were supposed to go to this big tour of a very popular Broadway play next month. I invited her and I've been excited since, working hard to save up so that I can go, and I was going to surprise her with a ticket and t-shirts for both of us as well... Well, yesterday we went to a local event together and she told me that she has another friend she met recently (very recently, as yesterday was the first time she EVER brought this friend up in topic of conversation)... And that she had invited the friend with (without consulting me), and that we could give her a ride in MY car.... She is completely aware of my condition and feelings on people I don't know, as she helped me through the incident mentioned before. She knows good and well that I'd NEVER be ok with that, yet she fully expected me to do a 2 and a half hour drive to a city I don't really know, with a complete stranger that I've never met before, in MY OWN CAR... Not hers, mine, in which I'd also be paying for the gas for the trip. This is also someone that she BARELY knows. Not to be overly paranoid, but this friend could do any number of weird/bad things in that time! I feel so shocked and hurt that she did this! I just told her that I'm really uncomfortable with that and that I wouldn't give her friend a ride, and she seemed so disappointed in me. After the event I dropped her off at home and had the 45 minute drive back to my house to think about the situation, and I ended up just saying that something financial came up and I can't go to the play. I didn't want to stir the pot anymore. She said that she and her friend will still go, so I guess her friend has a way of transportation after all… Am I just being a jerk in this situation? Should I have just gone along with this? Should I have suggested an alternative or found another solution?Am I wrong for just cancelling on my part? Is there anything else I should do in this situation? I am literally stumped here....