Sorry for not putting up a note. But here's one now.
Izzy's shield is really similar to Evey's but it's not based on the same thing. Now that Izzy has a gedutu bonded to her, it's kinda become its own thing. It still has the main shortcomings of the Mallet, which is that it's technically broken. But for the most part it's reset and adjust to Izzy. Even though it didn't change to her favorite color.
This is all to say that Izzy's constructs aren't limited by the constellation requirement of the Mallet. Just what she's limited by will ultimately be up to her. Even if it's only on the subconscious level. Izzy's already in uncharted territory with the whole bonded to a gedutu that came from another gedutu. So who knows what she can do. But she sure plans to find out.