Thought about it aswell, I dont think it work that way - the devil fruits are just like Akira Toriyamas Dragonballs, you use them, and they are gone for a while til' someone finds it again.
When it comes to "Who should get it" - I think the fruit must go to a person with routine and as Dagama said: there are lots of people who are searching for the fruit now and Blackbeard or any other haki user would defeat Rebecca if she doesnt get those years that Ace among others had to train for the attacks and defence.
Sanji as everyone says is the most clear for me, Rebecca just wants the fruit to defeat DD, which is a pretty clear statement that he will fall, by Luffy/Law or as a touché: Rebecca slaps him..
Downside if Sanji gets the fruit, he will have a great boost for the monster trio,