Try taking Bella outside on a leash to a specific area to potty. Stay outside for 2-5 minutes and lots and lots of praise and treats or toys after she goes potty outside. If she doesn't go take her back inside for about a minute and then right back outside to the same spot. That way you can keep the leash on her in between potty attempts at least. It may take going in and out several times and you can always stay outside a little longer, she probably has better things to do outside then go potty, but once she is back inside she remembers she has to go. Depending on where she came from it may have been normal for her to go in the house or where she was sleeping too, but she will learn and it sounds like she is going to be a smart one. Take her out about 10-15 minutes after eating, playing, drinking, or sleeping will help too. Sooner if she can't wait that long :)
Try not to play with her outside until she goes potty if you think she should have to go. Once she goes it can be play time. She is going to have plenty of accidents at her age because she can't hold it well and if you are playing outside or she has lots of times there are tons of distractions and things to sniff.
With ours if she went inside, I didn't say anything to her, just cleaned it up. If I caught her in the act I might pick her up and take her outside and then tons and tons of praise for going outside. We also used a special cookie, that she got as soon as she went outside and once she went it was playtime!
Good luck to you and Bella. It sounds like she is a smart girl and will probably learn quickly. Keep up the training and if you have the chance, I'm sure you already know, take a puppy class with her. They are great for socialization and training in a new location.