User blog comment:IamJakuhoRaikoben/Sorcerer Magazine, Issue 45: September 2015/@comment-94.71.39.253-20151004062152/@comment-5268982-20151004082803

My two cents:

@God But that sounds like a handicap-Wendy gets to use 100% of her powers, while Lucy does not :/ if both fighters have access to all their skills shown in the manga, then Lucy does get to summon him.

Besides, the argument about Lucy's personality is weak for 2 reasons:
 * If personalities also come to play, then Cana would probably obliterate Juvia because Juvia isn't interested in a fight that does not involve Gray.
 * Wendy would not have it in her to use DF against Lucy either. Hell, both of them would surrender if we took their personalities into account.

@Rai Summoning CSK is absolutely within the limits of Lucy's power. She summoned him herself, by breaking one of her keys. Mard Geer even stated that his disadvantage comes from Lucy being exhausted at the time.