How to house train my female Chihuahua?

I got Reecie about 5 months ago. She was an outside doggie then. We brought her home that day an started house training her. We would keep an eye on her and take her out when she needed to go. She learned quickly, within one week. She did good for about two months, then I took in a rescue female Chi. She was housetrained, but older, so she needed puppy pads. Reecie then started using them too. When our rescue went to her forever home, we took away the puppy pads. She did fine for a while, then started pottying in the house. So we told her no, then praised her when she pottied outside. She still didn't get better. So we put the puppy pads down again. She used those for a while then quite that too. We thought she maybe was doing this to get attention so we started showing her tons of affection ALL THE TIME.... It still isn't helping she's sneaky too, she waits until I go in the other room then hurries and pottys. What can I do? I've tried everything!!!! Thank you all in advance. :)