As Chantel has mentioned, chicken wire is generally too large (although I have seem some smaller spaced chicken mesh at TSC from time to time). You could go with the window screen material, provided you make sure its metal based and not fiberglass or plastic. You dont want them chewing thru & having escaped babies running around.
Good luck with your gal, and hopefully she's just going thru growth spurts & not an early pregnancy.
~Barb~
