Again - antibiotics take TIME. Lyme is tough to diagnose and to treat - I know several adults who are on 30 day antibiotic regimens, and many I know who have been through it continue with immune system support because the effects can be long-lasting. Not to panic you, just to have you be more realistic in expecting results. I wouldn't expect results in 3 days with something simple like strep throat, but if this is bacterial (which is what you say in your paragraph although the title says "virus") it may take longer. What miracle recovery are you expecting? And a virus isn't responsive to antibiotics anyway so I'll assume you just made a mistake in using that term.
I'm concerned that you have no confidence in the doctor. If the child's parents feel that way, they should get a 2nd opinion, or a third. Perhaps you are just getting agitated with partial info? While they may not mean to exclude you, it's understandable that parents with a sick child and medical info overload aren't going to relay every single detail to the child's aunt. Do you tend to be a worrier? Or are the parents also beside themselves with concern and frustration with how long this is taking? Look, THEY have to be willing to go to the next step, which is another pediatrician or a children's hospital with a team of people (gastrointestinal, maybe infectious disease specialists) who will address the whole child. If they are content, and there's no negligence on their part, then I think you have to be supportive of them and help in other ways than trying to solve their child's problem. Maybe they could use some babysitting or some home-cooked meals to help them - they must be stressed out. Try to help in the way that they need and will accept.