When I get to point I can have low fat cheese a s eggs can I mix in steamed spinach?

Sure

I'd say you can have those things when your specific programs says you can - it varies so greatly from one program to another I've noticed from participating in the forum for the past 8 months.

As long as it's cooked i can't imagine why not.

Spinach is very soft when cooked. I eat it raw too instead of lettuce! I can't see why you wouldn't be able to eat it, taking into account your portions etc and whatever nutrition plan you were given to follow.