Rachael & Andrew.
Rachael doesn't need to tell Andrew no, but I think she would be wise to make it clear she's not interested by pointing out what she does think. She can do this by friend-zoning him hard.
OK, so it's not all rainbows and sunshine being friend-zoned, but it gets the point across.
Andrew: I think you dropped your napkin.
Rachael: Thanks! You're always looking out for me. Like a brother.
Group conversation turns to dating, and Andrew is present.
Rachael: There's this guy I see at the coffee shop on my way to work. I'm thinking of asking him out. (Goes on for a sentence or two about this other man and how he suits her wants.)
If the GIANT HINTS of him being more like a brother, or of her interested in not-him go unnoticed, then I think it's fine to have a friend step in... casually, but firmly.
If Rachael and Andrew share a mutual friend:
Andrew brings up that he's interested in Rachael. Mutual friend says gently, "Andrew, it's pretty obvious you like her. I know you try to be subtle, but you aren't as subtle as you think. Plus, I don't know whether or not you realize this, and maybe you need to hear it... she's not interested in you as more than a friend."
Raphael & Andrea:
Same friend-zoning tactics. "Like a sister." "It's good having -friends- like you." "Oh, hey there's a girl at work I'm thinking of asking out."
I've never found women to be as clueless about these social clues, so usually that's enough. That's not to say that a woman can't overstep... in which case, I'd still suggest the mutual friend. But, that it be done quite privately, by a friend closer to Andrea to soften the blow.