I was in exactly the same position as your new student - adult, no musical background, wanted to learn clarinet. That was two years ago and now I'm completely addicted to it. I don't know how you teach children so I can't say what to do differently with adults, but I can say how it was for me if that would help.
My teacher told me that the expectations of adults tend to be so much higher than children's. Children don't compare themselves with virtuoso clarinettists, they just get on with making a noise. Adults, on the other hand, know what a good clarinettist sounds like and are impatient to get there. Also, adults may have started learning (as I did) because they want to be able to play their favourite music - so as soon as I could string a few notes together, I was trying to play like Artie Shaw

As a complete novice, I was totally ignorant about what it meant to learn to play an instrument. On my third lesson, I pointed to my Team Woodwind book and asked my teacher if, when I got to the end of the book, were there any other books to go on to or was it just a matter of skill after that

If your pupil asks you this, do try not to laugh, it
can be done, honestly - my teacher was very professional and chose his words very carefully when he answered!

During the first half term break, I was very pleased with myself because I re-wrote the notes of one of my favourite pieces into the lower register (I won't say transposed because I'd no idea what I was doing from a theory point of view!) and played it to my teacher the first lesson back. Funnily enough he wasn't as impressed as I was with it

He told me it wasn't a good idea to try and run before I could walk, that I should instead be concentrating on breathing, rhythm, tone etc, and playing at a speed to match my ability. Oh dear! The following week I was so disheartened that I didn't play at all - we just discussed some CDs that I'd taken in. I guess it was around that time that it began to dawn on me that I wasn't going to learn how to play the clarinet within the month or two that I'd originally envisaged

But once that realisation had sunk in, it was then just a matter of adjusting my expectations and starting to take it a step at a time.
The point of this rather lengthy ramble is to give you an insight into the possible perspective of your new pupil (although of course she may have a completely different perspective). Be aware that she may be leading a very successful life outside of her clarinet lessons, and that "failure" may be something that she has not experienced for a very long time. It is hard enough to step outside your comfort zone in the first place, without discovering that it is actually a lot more uncomfortable than you expected. But if she can get over the initial shock of finding out that learning an instrument takes years not months, then hopefully she will start to get more satisfaction and pleasure out of learning the nuances of the clarinet than she would have done if it had been something she could pick up in a few short weeks.
I hope you both have a good lesson, look forward to hearing all about it