Conflict of Interest?

Is this person employed by the facility as a PRN LPN and also doing something or other on the side for the physician as an LPN?

Or is she simply showing up at the facility and "rounding" supposedly on behalf of this physician?

Well, either way she is not allowed to practice medicine. And he is not allowed to delegate medical assessments to her. If either one of those things are what is actually happening it is fraud amongst other things.

Why does she have people's personal cell phone numbers? I wouldn't answer her calls, I can tell you that much.

I'd probably handle this by 1) NEVER entertaining any of her fake medical practice (such as answering her calls or taking orders from her or even responding to her if she is acting on the physician's behalf, etc.) and 2) informing your superior of anything inappropriate that you can substantiate--it must be rock solid and not hearsay or an assumption. For example: Say she calls and wants to know why xyz isn't done. You could simply inquire of your superior something like, "Suzie Q called here while I was on duty and wanted to know why X [brand new order] wasn't done yet. By what legitimate authority does she access our records when she is not on duty as an LPN here and question our care?"

(Remember that you'll only be talking to her in the first place if she makes a call to the facility/nurse's station; otherwise ignore her).

If you don't get an appropriate answer from your superior then you will have to decide about officially reporting this activity. Your place of employment has a legal duty to protect the residents from receiving fraudulent care if indeed that is what is going on.