I have never used Vectra 3D, and if I were you, I would never give her Trifexis, because it has killed several peoples bullies before. The only heartworm meds we use is Sentinel. We have never had any issues with it, and give it to all of our pups, and adult bullies and Frenchies. We don't use anything for ticks, as we are in an area where we don't have to worry about them. Sentinel works well for fleas also. Plus you have a beautiful pup.