Too bad. It would have been a perfect strategy.
Eh. Her ice magic sucks ass anyway. XD You gotta NUKE it with some flares, frogs, and lighting bombs. XD
Metroids are extremely powerful creatures, they are severelly weak to cold, their ONLY other vulnerability is concussive force like with samus' missles. None of the spells of Chrono Trigger use concussive blastwaves. In essence without Marle's ice magic or samus' missles they're screwed against metroids.
In fact the ONLY way anything other then Ice would work is if they receaved a heavy dose of Phazon poisoning. That would weaken their genetic make-up enough for something else to kill them... but there's no Phazon and not enough time to feed it to them for about... 5 weeks maybe for it's effects to mutate and weaken them. Of course, thats asuming they don't become imune and you give rise to another Prime Metroid. -,-
The monster known as Metroid Prime isn't an actual metroid. If you bothered to scan the pirate logs you'd have known that. It came to Tallon IV INSIDE the phazon meteor and is in actually a phazon based lifeform. In Prime 2 Echoes Metroid Prime returns to hunt down Samus and get revenge on her. At the end of Prime one you get a secret extra ending for having 100% item collection in which you see the puslating remains of Prime and then a clawed black hand with a eye in the back of it pops out.
Oh they are so screwed...