re: Looking for some advice/opinions please :)

I almost feel unqualified to answer some of these questions but please hear me out. I’ve had my cake business for 6 years and it keeps growing. I’ve made a lot of observations and It is in my personal opinion that learning the Business is a learn as you go type thing.
Have I ever had this problem? No, I wish. I’m sure that I like you have stood for endless hours until my feet ache and my hands cramp from squeezing a pastry bag.
Of course you need help! You can’t do it all on your own!
If I had to introduce a new cake maker in my business, I would keep it very upbeat and positive, “We are proud to announce the newest member of our team, Suzy! Suzy is very creative and has a natural ability and talent and we are very excited to see what new flavorful creations she is going to make!”
(Okay, so I’m not a writer I’m a baker but you get the point)
Personally I feel honesty is the best policy where customers are concerned. I am honest with my customers no matter what and I feel they respect me for that.

I understand where you are going with the hair dresser in training but lets look at it in a different light. Let’s say you were a builder building a house and you had someone apprenticing with you. You wouldn’t charge any less for the house would you? When I apprenticed in the bakery years ago, they didn’t charge any less for the baked goods I produced. If I messed up it got trashed and I did it over again until I got it right.
I feel that if you are giving customer the same quality and standard of cake you have always given them, then no worries. It’s a business run by a team.
Additionally, that particular customer that got perturbed when you had said you had someone new helping you?
I would work personally with that customer. They’ve been a loyal customer for quite some time and deserve your attention.
As a customer, If I was getting the same quality, taste and service as I’ve always gotten, I’d be a happy customer.
One little extra: I might think about making “Suzy” sign some kind of contract that states that my recipes are MY recipes that should not be sold or reproduced in any way. (Lord knows how much time we put into finding , creating, trouble shooting and tweeking recipes! )
Good luck to you, I Hope this helps, It’s good to see you successful you have become!

Psalm 127:1 Unless the LORD builds the house, the builders labor in vain.