Betray her

If you brake the bloodline chain it should brake the magic chain. You just needed to lure her closer. You know just how to do it. You lower yourself into a non-threatening position. You put on your saddest, most prophetic tone of voice. The one you have heard many humans use as they beg for mercy either just outside your mouth or from inside your gut. "You're right, I am lonely. I think I need a hug, will you please help me." You beg and squeeze fake tears out of your eyes.

"Oh, you poor, poor dragon. Look at you. Your scales are dull and scared, your horns chipped, your tail bent and are you crying." The girl replies falling for your deception. "Come hear." She said with arm outstretched and moved towards you.

The little girl approaches you and you feel your victory within your grasp. As she moves within range, you strike. Your long kneck extends and your head shoots forward like a snake. You massive jaws open and engulf her body. At her size, one gulp is all that is needed to send her down to your belly.