Mine are both housetrained, and Loki has diabetes insipidus (which basically means he drinks too much and therefore pees a lot) and Sammy wasn't housetrained at 1 yr old when we got her. So we've spent quite a bit of time on housetraining. Sammy only just caught on to letting us know when she needed to poop outside about a month ago. Tonight she even went in the snow!
Anyway, I some suggestions. First, have you tried a bell? Second, did I read right that she goes outside but she still has pads? I'm sure that is confusing her. Eliminate the pads and take her outside only. Also, make sure the carpet is treated with an enzyme cleaner, but also just because she peed on the carpet once doesn't mean she has to keep going back there. Mine peed on the carpet a hundred times while we were training, but they don't at all any more.
Sam was really hard to train because she thought nothing of going on the floor. We had to watch her every second and if we couldn't, she was crated or tethered to something. We learned what time of day she pooped and stayed outside until she did. If she wasn't interested in pooping she got tethered to the door and we took her out every 30 mins or so until she finally went. Otherwise, she would run off and go in the house somewhere. Now, finally, she rings the bell when she needs to go so we don't have to do that anymore.
And every 30 minutes is normal around here with my pee machine.