Once you come back in the house you need to watch her very closely, so you can catch her, to start her business. Then in a stern voice tell her bad girl take her back out immediately. Then once she goes make a big deal out of it and praise her and let her know she is your good girl. Once they have done their duty and you haven't caught them it is too late, to correct the problem for that occassion. You must catch them in the act, and some will hide from you. If that don't work I would try to keep her in a restricted area (I use a baby gate and my kitchen) see where her favorite place is in that area to do her duties, then lay down a piddle pad there. Let her get a custom to using that pad, once she has done that start moving it (piddle pad) to the closest door you take her out of. This has worked for me and some of my little doggies. Some catch on quicker than other, so yes you have to try to find patience with her but she will get it.
Good luck