User blog comment:IamJakuhoRaikoben/Sorcerer Magazine, Issue 45: September 2015/@comment-74.127.135.27-20151004010518

I think Lucy would win in a battle long as she used Urano Metria w/ Gemini at the beginning of the battle. Of course, it's possible that Wendy would be able to dodge or increase Lucy's power so that it was too great, as she did to Chelia. And if Wendy was able to go into dragon force, it would definitely be difficult for both mages. But since we have no idea what Wendy is capable of after the timeskip, I choose Lucy.