Firstly ensure to bring a stool sample immediately and test for coccidia, giardia, hook worm etc. She should definately be seen by a vet first and farmost if not already done (which I am certain you did). But be specific on the stool testing for the above.
Secondly, it is extremely important to keep her going to your parents house to ensure that she gets proper socialization. Again - ensure that she is free of any parasites or diseases prior to letting her interact with another dog.
Puppies take a while to house train. Time and patience. Frequent outings are required. Take her to the door and say 'outside'..leash her and take her out to do her business..then lots of over the top praising. They cannot control their bladder or bowls over extended periods of time as older dogs can.
I don't know what mix she is but she is absolutely adorable.
I would suggest getting pet insurance since she was purchased at a byb. Protect yourself for the future.