1. The answer to your first question is YES. You cannot stop any one from filing a case, albeit the case will be tested on the touchstone of law in the court. She can file a FIR against you by stating that she was promised by you that you would marry her, and taking your words on their face value she had sexual intercourse with you. In your defence you can deny that intercourse ever took place or you promised marriage to her.
2. She can file the FIR either from Bangalore or where she is residing right now depending on the nature of case she builds up against you. In all likelihood Bangalore is where she will file it.
3. You may be arrested at any time after FIR is filed. To obviate the sword of arrest which will hang over your head subsequent to the filing of the FIR, you should immediately seek anticipatory bail.
4. No employer, private or government, likes to have on its rolls an employee who is embroiled in criminal charges. So you may lose your job, more so if you are arrested. This is why taking bail becomes very crucial.
5. If the case is decided on merits it may take up to 3 years to be decided, albeit such cases are most of the time filed with the object of extracting fat money from the man, so it may be settled out of the court sooner.
6. As I remarked at the outset, you cannot stop her from filing the case. What you can do is channelise your efforts towards making sure that you are not arrested.
7. After filing of FIR machinery of law will be set in motion whereupon police will launch an investigation.