Ultimately, it's your money. Do whatever makes you feel better.
If you do decide to give it to her, make it a gift, not a loan. If she pays you back, then you can be pleasantly surprised. But don't hold your breath.
And I'm curious about one thing - how does the death of her grandparent equate to a need for money? Obviously, I don't know this girl, but in far too many cases the desperate cry for money means that her dealer isn't taking it in trade anymore.