Welcome! They can be very frustrating at times.
I would put her on the wee-wee pad and wait until she goes. If she doesn't go put her back in the pen. She won't hold it forever-she will either decide to go in the pen (on the pad) or next time you let her out she will go on the other wee-wee pad you have for her. Do not let her run away. Sammy used to do this and pee in other places I wouldn't notice till hours later when it got stepped on!
After I got so frustrated I followed my friend's advice I tried this with Sammy at the beginning and he started going on his own after about 2 weeks. Of course I'm no expert.
