This is a little therory I have...

In Broken Spell II, Udonna only lost her snow staff, while she used her wand to morph. Her Snow Staff was only her weapon. Plus, afterwards, she said she couldn't fight without her snow staff. She never said she couldn't morph. And once the other rangers came in, she probably figured 5 would be enough. So I think Udonna can still morph, but has no weapon.

Re: Udonna can still morph
 

That's a good theory. Granted she could still fight I'm sure since she could still use magic with her Wand, it just probably wouldn't be as powerful as her Snow Staff could dish out.

Re: Udonna can still morph
 

I think the Snow Staff was her morpher. So I don't believe she could morph. Even without the staff she could have fought with Ranger powers. But she said she couldn't so I doubt that she could physically morph.

Re: Udonna can still morph
 

If the Snow Staff wouldn't be her morpher (i.e. her source of power), she would've morphed into action for many times when the Rangers needed her.
She didn't do it.

It's kind of a MMPR thing. The Power Coins were the power source of the MMPR powers. This was clearly demonstrated in "Return of an old Friend, Part I". When the Rangers give up their power coins to Goldar, he tricks them and says that there are no more Power Rangers. It's the same with Udonna's Snow Staff. No Snow Staff... no White Mystic Ranger. The same goes for the other Mystic Force Rangers. Udonna transformed their staffs to cell phone morphers. You take those away, and you've got 5 powerless superheroes.