If you don't treat your yard she will get fleas all over again. Sentinel is strong enough. When the flea bites your dog Sentinel will kill it. When there are lots of fleas you can combine with Advantage who is topical. But if you don't treat the environment you are never going to get rid of the fleas. If I see ONE flea on Alex, the yard is treated. I almost never have to put something on Alex. That one flea I kill with my nails.