Hi all! For the last four years, I have worked as a vendor for a local artist. For me, it is a side gig that I enjoy doing. I made close to six figures during my full-time job on the week, and nearly every Saturday from 6 AM until 12PM I am selling at a craft fair on her behalf. I have traveled for her and she pays for mileage and food. I have done multiple day festivals. If I am available at the time of a festival and she asks me, I’m there.
In the last four years, I have only missed one event because I was sick the morning of.
Two other vendors have come and gone because they also have full-time jobs and they didn’t want any more Saturdays gone. The artist began giving advice regarding how to change our sales approach. That was when the last vendor left.

A few weeks ago, she was going to be vending out of town. Her show was canceled. 24 hours before my saturday event, she texted me that she was going to use this time to sit back and observe me. She assured me that I’m not in trouble she’s just always open for areas of improvement. I mentioned in passing to the other vendors who have known me for the last four years that this would be happening and they were pretty perplexed, assured me I did a good job and then I didn’t need to be babysat. They kind of tease the artist later on about babysitting me and she was offended and was like no I just want my business to be good.

That’s fine and dandy. But it turns out she was taking meticulous notes the entire time, ran through ChatGPT, and sent me an email that is equivalent to two full word document pages. The entire document is filled of ways I could improve.
I make $12 an hour for this woman. I do this because I like her and her jewelry and it’s just fun for me.
For $12 an hour, no matter what changes she suggests and I make, it will not make a significant difference in sales. If the time and energy spent critiquing me was put towards marketing, her business and online store, she’d be making online sales like crazy.

I’m currently frustrated because I feel blindsided by her critique. She gave great advice that I will be incorporating. But I’m looking for advice from an artist and how you interact with your vendors. If you have a vendor who sells on your behalf and you pay them $12 an hour +15% commission, would you find it acceptable to send them an email twice the length of this post full of critique?

UPDATE!

I responded to the email:

There is some great advice and feedback throughout. I do feel blindsided, though! You assured me that I was doing great, and you were just looking for small ways to improve. 
Instead, there were notes on every single person that came to the table that day, and every single thing I did or said. For $12/hour, 15% commission, and giving up 1/3 of my year’s Saturday mornings and Friday nights, choosing to working 6 or 7 days weeks in addition to my full time job, this was an incredibly lengthy email of critique. I understand the intent is to better your business, but this is excessive. 
This is micromanagement, and this is why two other vendors have quit. I’m not quitting! 
You need to be aware of this as a business owner moving forward, most people would receive this email and walk away. The technical feedback was great, but it was very jarring and almost offensive to receive. It feels like you took notes on every interaction, then ran it through ChatGPT for ways to improve.

I strongly believe your online store can lead to a huge boom of business. The impact and investment of focusing on online sales and marketing will significantly increase your revenue. The opportunity for growth from that aspect of your business is massive in comparison to any changes made to in person markets. If I was the perfect sales person and just a double of you, I could maybe make $150 more each Saturday. That’s not a very significant change to your income. But if we focus on marketing to people outside of this area and structuring online sales, you could see hundreds, if not thousands of dollars in increased sales.
I worked in retail sales at RETAIL for about five years, when I first entered the working world. I spent a year as a business-to-business sales woman for a company that worked exclusively with law firms. I have learned several additional, more objective, ways of measuring success that I think we should introduce. It would be incredibly helpful to see annual reports of- I do this for my job now, too. Senior account manager of POSITION, I write the contracts and oversee the timelines in the progress of projects to make sure everybody gets things done in the necessary amount of time, the proper amount of work, and that everyone is paid adequately. 
Let’s look at the numbers. For each vendor, how much revenue they usually bring in at the craft market? How many transactions are there? How many sales per transaction?
Is there a difference between my numbers, your numbers, and any other vendors numbers? How do those numbers compare to each other and how do they compare to previous years/months/seasons/festivals? What world events may have contributed to any changes to in-person sales? Emergency weather, Covid, Wars, etc
What are other vendors selling a similar product in a similar price range bringing in/paying out for vendors? What goals can we set and how can we manage this this time move forward and things inevitably change? 
I thoroughly enjoy working with you and will continue to do so until my schedule no longer allows it. Let’s continue to find ways of improvement together. I will absolutely be incorporating much of the advice given in your email. I would love to be an assistant to help figure out your online store desires and create a plan for that aspect of the business, too. I think it would bring you a more significant return than my personal improvements will make. I could be wrong- and now we know what numbers to look at so we can truly measure it!
Thank you for understanding! I look forward to seeing the numbers for EVENT.