NICE problem, Ghost Who Walks!
The alien is definitely dead? No hope of rendering aid? Then Gamma Girl--who's a bit like Nightwing, but with forcefield powers--quickly searches the body for ID, or anything that would help verify the alien's allegations about the Vice-President. She'd keep careful track of those screeching car tires, and once the cardoors started slamming and the running feet hit the sidewalk outside, she'd get the hell out, leaving the body of the poor alien behind to slow down or mislead his pursures.
Gamma Girl would do some careful poking around to establish whether the alien was telling the truth about trying to prevent the attack on the President; talk to people, do a little judicious B&E, review tapes and files of the event. Hey, I majored in snooping [(Streetwise (16-), Conversation (16-)] back in Snoop School! She'd be careful, because if he _were_ telling the truth, others on the Viper payroll might be looking for anyone getting nosy. And what if the alien _were_ trying to prevent an assassination attempt?
Then begins the biggest undercover operation of Gamma Girl's career; investigating the Vice-President for Viper connections. This would involve stealth, conversation, acting and a new intern on the White House staff. Fortunately, I majored in sneaking and spying [(Acting (16-),Perception (14-)] back in Snoop School! If Gamma Girl has proof--and time--she'd take her info to a well-established news magazine that wouldn't be afraid to annoy the government. "Village Voice" or "Rolling Stone"...both are liberal as hell, but at least they're widely _read_.
If Gamma Girl doesn't _have_ time (Viper is about to seize control of the U.S. and start another world war, or something like that), she'd have to overcome her CVK and take the Supreme Serpent down herself. Yes, it would mean being hunted as an assassin, but the world would be saved _to_ hunt her, and she could work to clear her name afterwards...for as long as she survived.