Because she runs away everytime, if you're willing to give it up for her, yes. If not, get a level 100 Trapinch from the desert so she can't run because of it's ability, but then it's another thing to actually catch her, and to actually catch a Trapinch with the ability, and when you can't switch Pokemon, but the choice is your's. If you're having trouble, catch it with the Master Ball, but just remember, you have to catch Mespirit aswell, and if on Platinum, you also have to catch the three legendary bird Pokemon.
Masterball. (Cresselia)
use it on your fav legend in the game =) OR ANY OF THE TRAVELING POKEMON MOLTRES ZAPDOS ARTICUNO MESPRIT CRESSELIA USE IS ON ONE OF THE THREE BIRDS which is what i do
I think you should use ur masterball on entei raikou or sourcune and maybey mew not mewtwo
I'd sugest Landorus.
Catch a Pokemon with it! I'd recommend saving it for Cresselia, as she flees from battle a lot.
masterball
I think you can use it on Cresselia because if you make Masprite faint in will stop running and you can catch is, but not Cresselia! I haven't figured out how to get arceus yet, sorry!!!
masterball or time ball
You should use it on cresselia or mesprit because they run away
other than a masterball probaly with a hacked ball cherish or ultra,timer,heal,and quick ball
You should use it on one of the 'roaming' pokemon, like Cresselia in Diamond/Pearl/Platinum.
on any legendary(just that it should be a strong or rare legendary)