My Grandpa is sick and not doing well. Can I get a POA on my Grandmother now in case he passes?

No Sandie. GP can't sign for GM. Only you can sign to appoint another as your POA. However, if your GP has a POA for your GM then perhaps she appointed someone as a secondary POA should the first designee be unable to perform at the time she signed for GP to be her POA.

Sandie, you don't "get a POA on" someone; it's an authority granted by an individual, at his or her discretion. Your grandmother would have to execute a POA or DPOA if she's able to understand the implications of it.

POA can not be reassigned, passed down or inherited- it can only be given by the principle concerned - unless a second is actually named in the original POA document.