Is my team strong enough to beat Cynthia?

I suggest leveling up your Empoleon, Giratina, and Electabuzz. If you are wondering why than it's, because cynthia has a milotic. You could use your Torterra, but just in case it faints you could use electabuzz. You should also add a dragon type pokemon as a special percaution just in case your other pokemon faint. If you don't feel like changing your team than I think you will be ok. Also you should buy a lot of status healers like hyper potions and revives. I beat cynthia and I didn't even use a single full restore or max potion.