Hey (love the name) Jackie Brown,
As a manager, I would not allow this. What is learned as a personal trainer during certification is quite different than group fitness certification, though there of course is some overlap.
That said: “could” you? Yes. Since there is nothing regulating you can’t. But, if the client is injured and you aren’t insured as a PT, this could come back and bite hard. For example: You “could” do your own taxes. An accountant is a professional trained in this area and pertinent laws. I’d trust them more…
There’s nothing wrong with doing what is best for the client and getting yourself certified for the future, which is what I would suggest if you were my employee 🙂
Yes, you need to obtain the proper personal training certification to work with individuals one-on-one. Although it may appear easy to just transfer the knowledge you have as a group fitness instructor, there is so much more that goes into training individuals. For example: Assessment and program design (based on individual goals), anatomy, kinesiology, behavior change, communication, health screening/joint issues, and special populations and considerations all just skim the surface. Not to mention liability.
So, if you are serious about helping others with individual training, look into an NCCA accredited personal training certification. There are many to choose from, and good luck to you.
Best to you,