Robin is spot on right.
Arm yourself with a Michelin 1:200000 scale map. You should be able to see the red N routes, these are all the equivalent of our A roads and will be in just as good condition. These will be useful to get you from A to B in complete comfort and quickly. They are also useful to link you up with assorted lesser and more interesting roads.
There will then be a whole bunch of yellow D roads. In the main these are the equivalent of our B roads. All will be solid and certainly rideable on a pushbike, motorbike (of any sort) and driveable in a car. These will wiggle about, probably up, over and between the passes, with hairpins - with inevitably a drop over the barrier to the valley below (it wouldn't be a mountain otherwise) - for sure and may not be 100% smooth, but that is why you are going to the mountains in the first place. Ride and enjoy them in complete confidence.
You will also see white roads. These will either be roads that fill in the gaps between the N and D roads or roads that run up to higher view points or ski villages. You will see that many are the same width as the the D roads, so dual track. Others are half the width. They will be just as you imagine, maybe in quite good condition maybe not. All will be rideable, just be careful as always.
You will then see some white roads with a broken border. These are probably unmade roads and sometimes tracks. Avoid them or try them..... I think you should miss them out.
What would I do? I would take the yellow D roads. Then, if I came to a white road with an unbroken border I would take a look at it and give it a go if my companion fancied it. If they didn't I would miss it out to make their day happier. Within a day or two you will get the hang of what the roads are like, what roads you haven't yet ridden (but can see on the map with all their squiggles and colours) are probably like and plan your next day's riding accordingly. It's the great thing about having a decent map, it tells you lots. The other thing you'll learn is how long it takes the pair of you to go from A to B to C to D. If bods make one common mistake, it's usually underestimating the distance and time taken.
The big trick is not to hype the whole thing up, making your companion fear the worse before they have set off. Most riders (and definitely their bikes, without a doubt) are much more capable than they think. If they are really uncomfortable, wet, cold, scared or just out of sorts for whatever reason then find the simplest, fastest route out.
You and she will have a great time, I promise.
