Now what in the world would make any of you think that I intend to 'interrogate' this girl? There will be no hot lights involved...she would certainly go running back to Billy and I would be found out!
My plans are to take her to lunch and nicely, sweetly, politely ask just what her intentions are towards my baby boy?

Nothing threatenting! I'm only 5'1", she's got me by several inches, and truthfully several pounds. She's not intimidated by my age either even though she will only turn 20 in a few days.
Naturally, I intend to be charming...we'll see where that gets me. I'll keep you all in the loop.
Don't worry, I'll be back for advice soon and to fill in the details.