I have a POA for my parents. The fact that you have a document does not mean that it's in force. IOW, there are conditions stated in the document which define when
your sister can assume the responsibilities. You can google for more information: when does poa take effect - Google Search
, so you'll need to read what's in the POA document itself.How
to sign the documents is discussed in this forum.
I'm not answering your question, as I'm not a lawyer. But, this is what I know about POA and wanted to be sure this aspect was covered.
Aside from that, asking an attorney is always good advice.
To some, the glass is half full. To others, the glass is half empty. To an engineer, it's twice the size it needs to be.