You have to look at her as if she is a baby and has no potty training. At 7 months old, she should not have free run of the house, she should be contained to whatever room you are in. Too much freedom is scarey for her, and she will never grasp training. If you plan to do outside potty only, than you are going in the right direction, taking her out every 20 mins, go for walks. Always give her a Positive Praise Potty Party when she does it outside and back it up with a small but yummy treat, I recommend using Peanut Butter Chips from the baking isle
Also, they
do regress during this as well
Mine weren't 100% trustable till they were 1.5 years old