There is nothing you can do to help your grandmother come to US. For a tourist visa, she must apply on her own merits, proving she has sufficient funds of her own for all typical tourist expenses, and that her ties to her own country compel her to return home timely. But her ties, her relatives, are in the US.
You cannot petition for a grandparent's immigration. IF your grandmother has a son or daughter who is a US citizen, and who earns enough to guarantee her support (including health insurance & all health care) for the rest of her life, they can file a petition for her. But not you. Her health issues could be a bar to her immigration, and she could very well be denied immigration on that basis.
You & other members of your family chose to break up your family & leave her behind. Now one of you go to her, or your uncle returns & takes care of her. But it is highly unlikely she can qualify to immigrate to US, and she will not qualify for a tourist visa.
Another consideration: for older people, especially those with health issues, relocating to another country is extremely stressful, and that stress can be deadly. It has happened many times that someone has sponsored an aged parent's immigration, even those with no apparent health issues, and they have had a major stroke or heart attack within days or weeks of arriving in the foreign country with their relatives. Trying to relocate your grandmother could be her death sentence. You need to figure out how someone can go to her & care for her in her familiar home, country, culture.