Hi again, A and thanks for your helpful reply.
I'm glad you already got Chloe checked out and she's fine!
Yes, the Bissel Spotbot works wonders on pet messes; I know this from personal experience.
If the aluminum foil didn't work, try placing a litterbox over that area. If that doesn't help, place a heavy duty plastic 'runner' over the area with the spikey side up. She will not want to walk or scratch on that material, to eliminate. Also, get a cat appeasing pheromone called Feliway which comes in both a spray and plug-in diffuser. It helps with inappropriate elimination and also helps to calm cats if they're stressed. After cleaning the area thoroughly, spray it with Feliway, but don't let the cats near it until it's completely dry--about 20 minutes. This will help her think she's already 'marked' there. Here is more information about Feliway, which is available in all pet supply stores and online:Feliway
Most cats will eliminate (urinate, at least) after eating, so if you're home, try placing Chloe on the toilet after eating and see if she'll go; if she doesn't, try about 10 minutes later and every ten minutes after that. Speak to her gently and remind her what she's there to do; repeat steps you took when you first trained her. Try to keep Cleo away from the toilet at those times, unless she really has to go.....you don't want her
to have an accident.
Please let me know how it goes after you try these suggestions. Thanks!