Mirabelle and the Haunted House (Mirabelle, #9) by Harriet Muncaster

Mirabelle's mum is a witch, her dad is a fairy and she is a bit of both!

When Mirabelle's pet dragon Violet goes missing in the woods, the sensible thing to do would be for Mirabelle and her brother, Wilbur, to stick together to look for her in the creepy abandoned cottage she disappears into. But the two just can't get along, and Mirabelle gets so cross that she says she wishes Wilbur would just disappear. She doesn't mean for it to actually happen though!

Can she sort things out and get Wilbur to come back? Thankfully help is on hand, as the cottage isn't quite as abandoned as it first appears. . .