Unless you have actually spent real time with her in person in some different situations you cant possibly make a realistic judgement on anything about her. If all you have to go on is a few snatched converstions and text messages then you'r going to filling in the gaping holes with guesswork and wishful thinking. it's a recipe for disaster... if you have given her lots of ammo that can be used against you then she has the upper hand and likely knows it.
Texts can and are discovered. My brothers wife was having an affair and he found out about it when he looked thru her suspiciously acquired 2nd phone...
You need to have a hard long think and unless you really know this woman and she is worth the extreme amounts of hassle an affair will entail then you should walk away asap.