User blog comment:Leek0421/The strongest Female Fairy Tail wizard/@comment-177.107.9.105-20151003000114/@comment-25324252-20151003003658

Lucy can summon at most 3 spirits at once. This means her opponent could deal with 3 and then by the time thats over, Lucy is basically out of gas and cant summon more. Her silver spirits aren't really meant for combat so if she is in a fight, she would rely on her gold keys, of which she only has 9 of now so pick your combination of 3. If she wanted to summon the Celestial Spirit King, she would have to break one of her keys, something I doubt she would ever do again after the emotional trauma breaking Aquarius's key put her through. Even disregarding that fact though, Hiro Mashima confirmed Erza and Mirajane are the two strongest females in FT, so moot point