Get a bog-standard non-smart one. You only need calls and texts. That way you cannot get caught out if some app gives away details.
Presume facebooks algorithms have found you with her - this article gives a bit more scope.
External Link/Members OnlyThough quite often its just a case of searching for your number on there if your settings arent as secure as you think.
When I'm researching a girl prior to meeting on SA - I'll check out a girl on all social media, and even if i only get a hit on Snapchat I can google the username or they've used a surname on there and bam I can search for the rest.
Its also worth noting that you can find people by simply searching for, example, Joseph then on the option just click the relevant city, say Preston and then its a case of looking through 100 people or so and you can find who you're looking for.
My advice;
Step 1 - get a punting phone. Basic smart phone on PAYG with no link to you at all. Set up a punting email (and social media is an option there is want to check up on people for security/verificiation) when signing up and have no link to your main phone. For anyone using AW, SA even online dating this is a no brainer - just gives you daylight between this world which can be more than murky.
Step 2 - go to your local cop shop and explain the situation. Someome in the SA thread has just had a similar scenario unfold. If youre married make this clear and hop :angelgirl:efully they'll just go to the girl and start proceedings - though later on you can drop the charges before they escalate things - just to shit the girl up and hopefully make her see the error of her ways and get her off your case. The punter in the SA thread mentioned the police where honest and said eventually if it goes to court your details will be in the public domain, not a risk worth taking, but getting the wheels in motion and you'll be able track the case online as it progresses and then simply pull out before it escalates.
I'm not a legal eagle so the police proceedures could be bollocks but I'd at least make these steps with the police rather than burying your head in the sand and hoping it goes away - or worse paying her and then she'll only come back for more in a fortnight.