
I think you're going to have to go right back to basics and treat her like an 8-week pup. Take her out after each play, after each nap, after each feed (she'll still be on three meals a day) and at least every hour she's awake. Watch her like a hawk - when she's awake, you're concentrating on her and nothing else. Don't let her go into any room if you're not there too. Maybe you'll need to take some time off work till she's learned.
Do you have a 'signal' word you use outside for when she's performing? And how do you clean up where she's been indoors?
As for her learning from your older dog - I've found dogs never learn anything
good from other ones - only bad things! Take care that your other dog doesn't reckon s/he can get away with messing in the house if the pup does it ...