Sharing design

I designed a sticker collection for a client to use just for personal use (to give to her students as an incentive…).
I want to know, if my client decides to share my work with a friend, am I allowed to ask her to lets say pay me more r to ask me permission before sharing it?
In other words, once I do work for a client, is it hers to keep or do I still have some control over my design if she decides to use it for other purposes than what she originally intended?

p.s. The stickers which I designed for her were made from her ideas and I just designed it exactly as she asked me to, so maybe that gives her more ownership over the design.

Hope I’m clear enough, I’d appreciate if someone can help me.
Thank you.

In this case it sounds like she has the rights to the design. Not sure exactly what you mean when you say she is sharing it with someone, but technically if you designed the stickers for her and she is printing them, she can print as many as wants and give them out to whoever she wants, unless you had an agreement that specifically stated otherwise. For future reference, you can clarify the scope of the design with the client ahead of time to avoid any confusion.