How can I get my Dog to stop pooping/peeing in her crate?

Just as simple as replacing the bottom floor tray insert. And when ever you want to feed or treat her, each and every time, say crate happily and throw the treat in but don't shut the door. Do this as often as possible, even replace feeding once per day for all day pieces of food for 4 to 5 days. And try to do it on your weekend when you don't have to leave for work etc. Then after a few days of that if she doesn't go potty if the doors open and just using it to be the "spot" for the treats throughout the day, then try either some peanut butter or maybe some wet dog food or if you feed raw just the good old hamburger meat, and smear it all over a disposable cutting board or snuffle type mat. I personally use a wood cutting board and peanut butter. Then place it in the crate and once she's in with the lick-em up tray, close the door but sit within eye shot for about 20 mins maybe 30 min. Then open the door and say "potty" excitedly and then immediately go out to potty and act like it's Christmas morning in the excitement department. And then once outside give one small treat say potty, then stand still in one spot till she potties. The reason I'm suggesting this method is it seems partially habit learned behavior and partially insecure territorial attempts. Hope this helps

Dogs usually don't poop where they sleep or in their sleeping area. This could be that your dog isn't getting enough time outside her crate. She is not able to distinguish her sleeping area / resting area with the rest of the house. She probably needs an open crate. This way she will go in her crate only when she wishes to sleep or rest. Of course in addition to that she must have walks for potty breaks outside the house, give her positive reinforcement for that as well.

It's time to lose the crate. Try a puppy pen with puppy pads instead. Keep a feeding schedule and potty routine. She will adjust with time. What she needs most is consistency. She will also learn behaviors from your other dogs as well. She may also be going immediately when she goes in the crate from anxiety. As a result of bad experiences with her prior owners. Please consult your vet. She could have something else going on that's unseen. I hope this helps, good luck. And congratulations on your new puppy.