Hi, I'd like to help you with your question.
It sounds like your granddaughter is in love with this man who has either convinced her to quit school and be with him or she has decided this on her own. Either way, the relationship she is in has somehow had a pull on her that school and completing her goals have not had.
This may be an obvious question, but has anyone in the family talked with her and asked her why she is doing this? The reason she gives could be a good hint as to what is going on with her and why she made this sudden change. It could also give your family some direction on what to do. For example, if she says she hated school and decided that this was a better choice, then it may be that she found school and the responsibility too difficult but didn't tell anyone. Then when the boyfriend appeared, she found a way out from the pressure.
Since your granddaughter is an adult, you cannot force her to comply with your wishes. I know it is frustrating for the family to not be able to help her that way. But you can do some things to encourage her.
One, try talking with her again, this time as a group. A sort of intervention. You may want to have a therapist involved for this as a mediator. That way, the intervention can go fairly and no one loses their temper or your granddaughter does not feel confronted. Here is a good guide to how to do an intervention:
http://www.mayoclinic.com/health/intervention/MH00127 - although this one is for addiction, it can be used in other situations.
Two, you can start allowing her to take responsibility for her bills. Let her pay her own phone bill, rent and student loan when it comes due. This way, she understands that her lifestyle is not going to support her needs in life. It may help her see that she needs to do more to take care of herself. And if she fails to pay her bills, she will be held responsible. Which is a good lesson for her to learn.
Three, make an attempt to get to know her new boyfriend. This may not be easy, but if you try accepting her choices (while still allowing her to be responsible for them) then she may be more willing to see things your way as well.
Family counseling may also help all of you find ways to cope with her behavior and give you someone to turn to to help you deal with the stress of her lifestyle choices. To find a therapist, ask your doctor for a referral. Or you can speak to your pastor if you attend church. You can also search on line at http://therapists.psychologytoday.com/rms/.
Let me know if I can help any further,