hiv is dead in air and saliva so you don't have to take any precautions to protect yourself from dead virus. In fact oral sex is not a risk for hiv because of the above so if she always uses a condom for vaginal or anal she has no risk.
Only non sexual risk is quickly sharing hollow needles that you use to inject with so you should move on from hiv fears.
None of the posts you have seen have a bias. Scientific facts are not "biased."
You cannot get HIV from someone just because they are dirty. You cannot tell if someone has HIV because of how clean or unclean they are.
While there is no way to determine if your sister has HIV or not, you cannot get HIV from sharing a living space with her. HIV is transmitted by having unprotected anal or vaginal intercourse, or by sharing intravenous needles with other people. You will not get HIV any other way.