With some research, I've concluded that, unfortunately, the ability Sweet Veil doesn't have an effect when the Pokémon is waiting to be sent to battle. Sorry about that. It only works on itself in single battles, or its allies in double or triple battles, and only takes affect when the Pokémon is on the field directly. If it is not on the field, Sweet Veil will not be activated.
It also doesn't have a affect completely outside of battle.
Hope I helped! Also, I think rephrased the answer slightly, to better answer the question provided. If it still isn’t answering it though, please let me know, and I’ll rather do more research or hide this answer.