Just grab her by the arm and tell her to smile for you. After she does so express approval and mention that her teeth are whiter than half the broads in this county and that you'd like to take her to knob hill and kiss her hands

I'm afraiiiiiidddddd, she's so nice and I'm worried she won't want to talk to me again....

Think of what Roman would do

Then do the exact opposite

Why in the world would you wait until she is about to leave to ask her out man?

probably should have pulled a "hey we're coworkers and you're leaving let me take you out to lunch" to gauge her interest around the beginning of her last week.
Does she even know you like her?

I'm a bit more anxious than usual, because the three of us hung out on Wednesday all day, but I was very upset that we might not do something like this again, and it really got to me; I ended up crying when they were driving me back to my car and I stayed silent when they asked me what was wrong.

I texted both of them when I got home, apologizing for it, both said they were just worried. Haven't talked to her since.