I know this is old but October just started so maybe you still need suggestions
First, we dog sit a lot and have brought many other dogs into our house. We always take them outside and have them meet and then come inside. We rarely have any problems. I would just watch any areas are "Layla's" areas, like her bed and maybe her favorite spot on the couch if she has one. Franklin and Maggie tend to get grumpy if dogs go near their stuff too so make sure toys and bully sticks are put away. Of course, Franklin and Maggie have gone many places with me and we used to go to the dog park every day so they are used to being around strange dogs.
For the marking, you could get a diaper to put on Paris so even if she does mark, your carpets won't be ruined. You can buy disposable ones that work just like baby diapers at any pet store, and probably even Walmart. I would keep some enzyme cleaner (and maybe a blacklight) on hand incase she does start marking though! That way you can clean it up before the stain sets. I've used both Simple Solutions and (my favorite, because of the $) Petzyme and both seem to work as well as Nature's Miracle.