You'll be fine, OP.
Similar experience. Wife's idea of outdoorsy had always been cutting through the Bass Pro parking lot to get to Starbucks. In 35 years of backpacking, she came along exactly never. Which was great for both of us.
3 years ago, out of the blue, she asked to come on a Colorado trip after I'd bought a RTT a few years before. Like you, a quick mental checklist of what this was really about netted zero........... so I said sure thinking this will be interesting and likely a once and done.
Asked for advice on multiple forums, got a boatload. Two responses in particular were from women who, like my wife, originally just wanted to know what the heck it was all about. Both said they immediately connected with the Starbucks comment and gave just the greatest advice to a dunderhead when it comes to camping with women.
So, fast forward to Silverton Colorado in mid-September 2017. Daytime highs in the 50's, lows in the low 30's. Rain. And more rain. And then more rain. The women told me to get a good French Press and learn how to make her a good cuppa coffee. Had some other thoughtful ideas that I'd have never thought of (hot water bottles on her side of bed before turning in, etc.). The weather insured it wasn't a fun trip, but it was real. The scenery, however, was spectacular. Aspens were in two-thirds color.
So after 6 days and somewhere around half way on our way back home..........she looks at me and says it was the best trip she's ever been on and if she could come along again.
Do you remember when you knew she was the one? Happened to me twice. 37 years apart.
You'll be fine.
Just make an effort.