These nails look like my mum's she is also on meds, So has very hard nails that shatter when knocked. I can't see a major problem with using this lady for your model. Just make sure she doesn't knock the enhancements because it could cause her natural nail to snap if they are very brittle.
These nails will be very difficult for a beginner to make look beautiful and with virtually no side walls to some of the nails, will not be easy for a beginner either.
I think attractive results are so important for a beginner's confidence. Still, they can be enhanced and I know you are finding it diffficult to get a model.
:!: You could always put up a post in 'chit chat' and ask if there is anyone who would be willing to be a model for your class who lives in your area? Some have done this very successfully using this site. No harm in trying. A model with more regular shaped nails would be easier for you to practice on and give a better result. :!: