Visitor visa for elder sister

[peaceful_bliss]

I am sponsoring visitor's visa for my elder sister who is 49 years old. She was widowed 21 years ago and worked as a middle and high school teacher until 2011. Now she has taken a break due to family commitments. She has a married daughter and a grandbaby.
My mother is deceased and my father is bedridden who is also taken care of by my sister along with my brother. I am a green card holder, employed full time in IT and I am sponsoring her trip and stay. I have some ongoing issues with my marriage, health and my child who has a disability. I have a letter from my doctor as well as my child's in support of my sister's visa application to visit me for 3 months to support me during this stressful time.
Should I send these letters and ask my sister to explain the situation to the VO?
Should I write the circumstances clearly in my letter to the visa officer as well as in my invitation letter to my sister?
What else do I need to provide other than the required documents that would help convince the VO that I need her help and she is the only one in my immediate family who can come.

The last time I applied for her visa was through my husband's H1 to visit me during delivery, but my husband advised her not to say the real reason but say that she is coming here for sightseeing and tourism. Her visa was rejected that first time.

Please advise.

Thanks

[peace999]

They absolutely will not give her visa to help you out in daily life. It is the same thing as in pregnancy.
They expect you to hire someone from US .
Even more important than that is the lack of ties in her case. No spouse, no work . Spouse, children, work and good income are the 4 things they look for.

If she could show strong income from her stable job in India, a history of foreign travel, and applying with her daughter's family to visit you on her own funding, she could have a better chance.