I would SCRAP the shop. It seems like you avoided the shop in town because the said person worked there. So you did not know if she STILL worked there or move to a different store . Which is what she did. She too had reasons to avoid you at any cost. Moving out of town was the best she could do for the situation.
You entering the "out of town" restaurant brought back memories to HER. Which is why she avoided you. 25 years, in her eyes, is not long enough. You entering the store as a normal customer did not remain "normal" , once you realized that the Associate was someone you know from a past experience. You completed the shop as you should have, regardless of whom waited on you. If you were in "HER" line and she moved to do another task rather than wait on you, that does affect your timing. Especially if someone else had to wait on you.
You complete your shop and leave the store. Yes, the "FEMALE" probably did go into her Chatty Kathy mode with her co-workers. Now that will probably affect your Report. Depending on what you write objectively. The Retail may question anything you write, negative or positive. She may not of known you for a MS then, but she will know now.
SCRAP the report. Called the scheduler let them know that you knew someone in the restaurant and as much as you try, you could not write an objective report. I would not tell the MSC about your past with the Employee because it is none of there "professional" business. If it comes back later where the MSC found out or knew you had some "personal" affiliation with a client's retail it may bite you in the backside and prohibit you from certain or all shops. MSCs do talk amongst themselves about common or shared Shoppers. Money may be why we are in this but better service is at the top. If your "lost" is less than $50 then everything will be alright . You may just find a better shop for a real bonus. SCRAP the shop, the report and the chain.
Some things PRIVATE should remain private, even on a public forum such as this.