If that really happened, I don't understand why the lady wouldn't just go to LE with her story; she'd still have anonymity-- that's what tiplines are for.
Because it wouldn't be fair to expect that some random elderly woman would have better grasp on do's and don'ts of missing person's case than everyone around had?
Press urged her to call Fran, not cops.
And that mention of anonimity may be just one additional form of control.
Not for the woman's sake, but to lower the risk that cops will hear anything straight from that elderly woman - and that even if she will come forward with additional info, she will give it straight to Fran, and with "promised annonimity" won't find it odd that no cop will show up to interview her.
Even if girls were at the mall, they weren't seen as first page worthy news, and no tip lines or detective numbers weren't spreaded as conntact info. Fran was. Most crucial time, as people were most likely to remember anything and feel confident enough to report that, it was all under strict control of Fran and whoever she was covering for.
Could be that girls never made it to the mall and she was trying to convince everyone that they were.
But could be also that they were there, and she was doing whatever she could to filter out all relevant and genuine sightings.
Sighting from the record store, real of fake, seems to be convenient - far from locations related to them, in alleged company of someone they haven't cared about.
But if they were involved, and if sighting from elderly woman was accurate, that would mean extremely dangerous for them, and they had no control over clerks, clerks knew, clerks could report that to cops as well, they could try searching for the woman - how to prevent the disaster that could come with woman being showed some pics of creeps related to Arnold's family? Get to the woman first, ensure that she will not come forward and conntact cops - kinda exactly what they did.