Clean Sweep by Ilona Andrews

"On the outside, Dina Demille is the epitome of normal. She runs a quaint Victorian Bed and Breakfast in a small Texas town, owns a Shi-tzu named Beast, and is a perfect neighbor, whose biggest problem should be what to serve her guests for breakfast. But Dina is... different: Her broom is a deadly weapon; her Inn is magic and thinks for itself. Meant to be a lodging for otherworldly visitors, the only permanent guest is a retired Galactic aristocrat who can't leave the grounds because she's responsible for the deaths of millions and someone might shoot her on sight.