Are these end of life signs?

Here's a thought...if she is combative (per your profile), not drinking, having diarrhea in this heat...that all adds up to a 911 call in my book.

Once there, talk to the social worker about hospice; the weight loss alone should qualify her.

My first recommendation was to bring hospice on board, but in your profile you say that your 101 year old grandmother doesn't qualify for it. I mean REALLY??? If a 101 year old doesn't qualify for hospice I don't know who would.
Yet your question says she's 90 years old. That's a big discrepancy. Regardless she should qualify for hospice, so I would certainly try getting hospice on board again, even if you have to try a different agency.
Remember though that even with hospice on board if she is at home, 99% of her care will fall on you or other family members/caregivers.
Yet if hospice feels her time here on earth is close to coming to an end, you can have her brought to their hospice home, where they will care for her 24/7 until she passes, and all of that will be covered 100% under your grandmother's Medicare.
Hospice will be better able to give you an idea what is going on with her, so please contact them ASAP.
Best wishes.

Is hospice involved? That's who can best answer this question.

I just read your profile. Who says she doesn’t qualify for hospice?