Should I grow my employee or find a new one?

I’m an event designer and would like to find a lead designer so I can focus on new areas of growth in my business.
I have 1 part time designer who has some growth to do in self-assurance. She is often overcome with insecurity that manifests as negativity and defensiveness.

I care for her and want her to see her talents, but I also realize she is not fulfilling my needs right now.

But she is talented, and over the last three years, I’ve tried out about 5 designers that did not come close to her expertise or realized they don’t fit the event industry.

I go back and forth between being thankful for her skills, and wanting to see if she can grow.
And just wanting to move on with it and find someone else.

What do you do in the case of deciding to attempt making ‘okay’ to ‘great’. and I’d appreciate your thoughts on giving up on what is in front of you in search of something that may be greater effort to find.