Do you find her resistant to thinking generally, or is it mostly with regards to math?
I'm assuming your sig is accurate, and we're talking about a 7 year old here.
Most kids I've encountered that age will engage when presented with appropriate material with a reasonably positive and supportive teacher. Where do you see her practical math abilities? Is it possible that there's something here that in unnecessarily hard for her?
First, go through a reality check - where is she developmentally compared to typically developing peers:
Second, discuss with the teacher the environment for learning math. Is there a potential barrier to her learning?
If reading and writing are easy and math is (too) hard, of course she's going to chose the reading and writing during free choice time. That makes sense. By all means, do the games and activities described above, but when a child of mine is acting like that, it's always been traced to be too hard. The underlying cause is often surprising, and has required evaluations by experts to accurately describe.