I think it's the item from Rocking Out. But another option would be that in Runescape Classic, women used to be able to have beards. Soem time after, it was changed, but the accounts which still had beards, didn't get them removed.
Though I doubt that this account is one of them, since it's VERY likely that she would've changed her appearance.
The beard is a disguise from one of those desert quests. I think you can only have the beard while you are doing the quest, afterwards its removed from you. Im guessing some people do the the quest halfway and stop it so they can keep the beard disguise.
It used to be possible in Classic by using WPEpro, and editing outgoing packets. I don't think it works anymore, not since '04 when they introduced rs2.