how to get a returning dog to pee/poop outside instead of on my carpets?

Definitely crate or confine the dog to a small area. Clearly not properly house broken. Make sure you Fully clean any soiled areas with pet cleaners with enzymes (like Natures Miracle). Must saturate down to padding and let dry with fan for couple days. House cleaning products (ie: Oxy won't do the trick). Go to pet store for cleaners.

I would recommend using a pen on hard floor or crate as opposed to locking a dog in a kitchen or bathroom. Any size dog may cry, bark, protest etc and can chew fixed furnishings such as the cabinets, trash can, shower curtain, wooden or plastic trim/edging etc.

Definitely restrict food/water prior to bedtime, and confine her to a small, safe area. If the dog is crate trained, great. A pen is also a good solution, or gated into the kitchen or bathroom or some other area without carpets. The smaller the area, the less likely the dog will potty there, since they instinctively don't go where they sleep. If you don't have a crate/pen/gates, you can tether the dog somewhere safe with a short lead (enough to turn around, sit, stand, and lie down comfortably, but not long enough to take more than a couple steps in any direction) to restrict her ability to roam the house and find places to go. Put her bed there to discourage pottying. In addition to restricting her access, you could also try setting an alarm for a couple hours after you've gone to bed, and take the dog out again then and repeat until she decides to go.

I find adequate exercise to be the best solution. Nothing moves the bowels better. Get her to the park/dog park, wherever she can really stretch her legs for more than 10-15 minutes.

Do you take her out on leash in your yard? Some dogs can be weird about toileting on/off leash.

I would strongly recommend crating this dog overnight. I utilize crates with almost all my boarders and try to make this clear to owners before they book with me. Pretty much all the dogs are crated when left home alone (8-10 hours/week), and overnight crating is based upon my assessment of the dog. If I'm concerned about toileting or destructiveness, they're crated overnight. If you don't have a crate, can she be safely penned in a room with hard floors? Clean up is so much easier that way!
Also make sure that her food/water is limited close to bedtime. You could also maybe try taking her out in the middle of the night, but if she won't toilet in your yard, that might be an issue. Did the owners say anything about potty pads? I'm not a fan, but if she's reliable on those...

Are you familiar with clicker training? One of my boarders was/is notorious for going 10-12 hours between toileting (not for want of opportunities!). He wasn't even really going on walks. Thankfully, his housetraining is really reliable, but I still don't like him going that long. I started click/treat for peeing on walks and saw almost an immediate upsurge in the number of times he would go. This should work in the backyard as well.

You can also feed her in the areas she normally has accidents. That will help her learn that she lives in those areas: they aren't for pottying.

Good luck!