There really is the point of view that says - this kid may very well grow up unhappy and after the newness of the situation has worn off, your daughter may end up not being a very good parent for the usual reason - she's only a kid. So you end up with a troubled kid and a more troubled grandkid. Unless you yourself are morally opposed, it really should be discussed with her. This kid will certainly displace another in the future who could be raised under better conditions.
IMO abortion is a perfectly acceptable solution, but the message from society is that you are a murderer if you do that. She may actually want an abortion but fear being villified.
Also, you must feel rather guilty about it yourself, as if you failed - well don't. That accomplishes nothing.