Any suggestions that can help me and can I be her guardian if the daughter-in-law don't want to?

I have an elderly client 86 and her husband is very ill. I have been there caregiver for 4 years they live less then a mile from them and never come to see them I have maybe seen them 6 times in 4 years. Her only child died and she will only have step children involved. The grand daughter whom has been named as executor of there will 2 years ago came over and had them sign power of attorney for everything until I got calls from ssi and the life insurance company wanting to take the insurance out of the estate and put in her name.. I told her to fix it because I would turn her in for elderly abuse, I haven't seen her since. But she is still in play . when the husband started getting ill they asked my client what they where suppose to do with her when he died.. We just don't trust them and would like to get a guardian in play before anything happens to him. Any suggestions that can help me and can I be her guardian if the daughter in law don't want to.