I've spent more time at strip clubs than I have with escorts,but I've seen the same happen -- i.e., Facebook somehow suggests them as friends.  I've never bothered reaching out to let them know; dancers seem far more cavalier about divulging personal information than escorts do anyway.

It used to be just the email you signed up with for Facebook.  Now it may suck in other email accounts you have associated with your Google account...or whatever browser you are using.  I am not a techie so there is probably more to this.

Not everyone agrees on this, but I would most likely try to make her aware of the problem ... before it becomes a BIGGER problem for her. (Some guys are concerned about blowback: accusations of being a stalker or worse.)
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Tell her to read the TER boards, mostly General and Newbie, and search for "plague" or "tentacles" or "nefarious." Those terms often show up in threads about "Avoid Social Media Like The Plague That It Is."  
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SM's self avowed purpose is to connect everyone whether they want to be connected or not.

Don't do it. It's not worth the shit storm it could bring upon you. Anyone on FB should assume their info is out there for the world to see.