I don't want to talk to her about the car, because she doesn't know that I'm buying a Tesla for her yet. But I know that she loves the car, because I've been taking her to car shows to secretly find out what she likes (Model S was her favorite, beating out the BMW i8). Also it's a bit too late to change my order now.
She sat in my Lamborghinis countless times before, so I think she's okay with the performance. She's driven my other sports cars just fine, too. I just tell her to not step on the gas pedal too hard if she doesn't want to go fast. Her only complaints with the Lambos are that they're too loud, have no trunk space, have no back seats, eat too much gas, and that they get too much attention. So this car is perfect for her (she liked my Bentley CGT, too, but that thing's also a gas guzzler).
As for being uncomfortable with the cost of the car... yea, that's why she likes cheap beater cars. But I think life's too short to be worrying about every little door ding and scratch. Back in my early 20s when I was driving the LP560, I was babying the car all the time and worrying about where I park it. Five years later, I'm parking the LP700 at Walmart, Disney World, and Universal Studios without a care in the world. Sure, people sit on my car and leave scratches with their pants buttons/belt or they write their names on the dirt on my car with their dirty fingers. But I don't think they'll be doing that with the Tesla.
I'm paying for her insurance, so that's for me to worry about (everything's going under my name, because I'm already past my gift tax exemption).