I have taken my wife. She even took the FF course at PSU, bought all the stuff, etc. I took her out a few times. She enjoyed each outing. But she didn't keep up with it.
She doesn't have the patience for fishing (or is it with me?, lol). After about an hour she gets bored with it, even if she's having success. She still sometimes goes with me and hikes, looks for bugs and frogs, etc. while I fish. She likes that better and I'm cool with it. They only problem is that it limits me on time and location. When she's along, my fishing trips can't go more than an hour or two, none of those all day events that take an hour or two just to GET THERE.
But what to expect? Hmm, don't expect to fish yourself for a while. Take 2 rods. For me, it was let her fish one rod while you get the other ready. Soon, she'll be in a tree or tangled. Hand her the other rod, and go to work on the one she was using.
Coaching is tough with a significant other. If you let her be, you haven't given enough advice and guidance. If you try to coach her, she gets mad that your looking over her shoulder and not letting her do things herself. Danged if you do, danged if you don't.