The doctor was "talking about" having a surgeon in for a consult? And did that happen or not? I'm assuming not since you don't mention it again.
I'm very surprised they were willing to send her home. I would take her to the ER now and say you want an MRI and a surgical consultation. Now. l question why they did not keep her in the hospital for observation.
Do not go just by the "jump test" or lack of a fever. My daughter did not have a fever with her appendicitis. And the jump test may help but every person is different and it may not be as effective with her. You say, yourself, that she may be masking her pain out of fear.
My daughter had appendicitis that also did not turn up on an ultrasound, but they then took her immediately for an MRI as well. It still did not "show" as a swollen appendix but they consulted right away with the surgeon and he said he would see her the next morning and they kept her in overnight. She had surgery the next day based on the surgeon's recommendation and she did indeed have appendicitis.
You do not have to have constant, screaming pain for it to be appendicitis, nor do you have to be vomiting a lot.
They also said that "if it ruptured, she would feel some relief"? But did they tell you that if it ruptures, she must be rushed immediately to the hospital because a ruptured appendix spreads the infection quickly?
I'm not sure what the doctors really want you to be doing at home observing her other than see if she gets worse, since it sounds like she is not truly getting better. I would call and say you want to see the surgeon right now and get a decison made. The surgeon may be the one to make the call. I"m not trying to be scary here, I'm just wondering what their protocol is and why they are just saying what sounds like "wait to see if it ruptures"--?