I think you might need to consider who your likely prospective customer base is (not just who you want them to be, but who actually is using these services in your town specifically.
I’m a millennial woman, and I would avoid a service advertising karaoke and light shows. I want to sit in a car with a driver who doesn’t talk to me, or who makes very light conversation. I’d take a worse car to get that. I typically take a lyft because I like the convenience of scheduling through an app, but I’ve called a car service when my flight arrived late at night and I just want to get home, in which case the sole deciding factor was “can you be here in 10 minutes?”
There are plenty of people who probably like the idea of what you’re selling, but if those people aren’t in your town looking for rides, then you’ll either have to figure out how to convince people to want what you’re offering, or you’ll have to change what you’re offering.
I manage a similarly rigid employee. What I have found works for us is having a written approval authority matrix about alternatives that can be offered, and if additional approval is needed, who can approve. People are more conservative in their thinking when they aren’t sure what is specifically allowed (or required) - it makes sense to me, you don’t want to approve something and find out later it wasn’t OK. By documenting boundaries up front (including what is always acceptable and what is never acceptable, and what the middle ground looks like), my employee is empowered to know what they can do. They will still sometimes roll their eyes about something being requested, but so far they’ve been able to set their personal feelings aside to offer what I’ve asked them to.
I would respectfully ask you to consider whether you’ve been specific enough in your expectations with your employee to start formal performance plan stuff. My impression from your post is that you’ve said “be flexible” without being clear about what you want - and I can imagine that being a scary position for an office manager who is typically expected to care about the bottom line.
I could be off base, but I also get the impression that you, yourself, feel a little bit uncomfortable standing up for your prices. Sometimes being perceived as expensive (even if you’re comparatively not) can make for uncomfortable conversations with clients, but if your business is going to be successful (whatever that means to you), the line has to be drawn somewhere- and having a clear understanding of where that line is might help you as much as your own employee.