<human>: Condense the text into a few key points

As a present for my 18th/19th birthday, I asked my parents if I could go on a road trip abroad before I start college in the fall. My Dad, who is the sole money earner and worker in the household, said yes and we decided to go together. 

We don't want to bring my mom since she has very expensive tastes and the trip wouldn't be possible if she came, since she's very dominating and would force my Dad to stay at luxury hotels and dine in very expensive restaurants. Meanwhile, me and my Dad prefer going to motels and traveling cheaply, road-trip style.

We have tried to explain this and she is refusing to let us go. I'd understand if she felt left out but the ironic thing is that she forced me to stay at home (including during my birthday) while she went on 4 very fancy vacation trips without me, and sometimes without my Dad too. Sometimes she even booked these trips without my Dad confirming it, despite the fact that it is his money.  

I've tried to deal with her calmly and rationally, explaining that it wouldn't be her kind of trip and for money reasons but she is refusing to let us go, unless she comes (consequently meaning the whole itinerary will have to be changed). At the moment, me and my Dad are keeping quiet about it, because if we mention it she flares up and gets very aggressive.

I'm considering just buying the non-refundable airfare so that way we 'have' to go, but I know she will be outraged about it all. For money reasons, it is not possible whatsoever for her to join us on the trip. How can I deal with her and make it a pleasant trip?
<bot>: My mom is spoiled and is refusing to let me and my Dad go on our last trip together, despite the fact that she often leaves me to go on vacation, how can I deal with her?