It’s always exciting to feel that spark of connection with a fellow witch, especially in places where outward witchiness is rarely seen!
As for how she knew you were a witch- that’s a great question, and Benjamin and Francisco gave some wonderful answers. Just a thought, but it could also be that she is able to read auras (here’s a post exploring people’s different color energies). Those with this ability can see the colors and auras of people around them.
Like Benjamin said, the static she mentioned could be from stress you are holding within you. It could also be some kind of internal energy blockage or mental wall you have to protect yourself from outside forces 
As for continuing to talk with her, I think you are very wise to watch from a distance and trust your instinct. Witches are people and we all know that people vary immensely- there’s no rule that says you need to befriend every witch you meet! Trust yourself and do what you feel is best 
Blessed be, Nicole! 