You did not say how old she is, but sounds like puppy behavior?? It just sounds like she needs to learn how to live in your home. Getting frustrated with her is going to rub off on her.
I love using "time outs" to give pups a message about what is appropriate and what is not. Some people think it does not work, but it does if you do it consistently. Every time she does something that is not appropriate, off to jail .. only a few minutes. And back in if the behavior repeats. They do get the message.
I am a bit concerned about the fact that you said you can barely afford to feed her. Do you really need this responsibility or are you just doing it because you feel so badly for her? You might want to consider a rescue, but if you do, please make sure you check them out thoroughly. You would want someone who would work with her issues.
You are not a bad person...some pups can really be trying. I know as I have taken many in over the years and some have been a bit testy.
