The package says cook from frozen, do not thaw first, but the lasagne is thawed (my daughter brought it up for us) and has been refrigerated for a couple of days. Is it safe to cook and eat?
This issue has come up in our home. We did an experiment with a frozen homemade and a frozen store bought lasagna. We defrosted both of them for 3 days in the refridgerator. We did this to make the process of heating them easier, as it takes a much longer time to heat them up frozen. They were both approximately 10 pounds each and took an oven each. We heated them covered up at 325 degrees for about 90 minutes, and the last 15 minutes cranked up the heat to 400 degrees uncovered to give it a bit of a crust and also added more fresh cheese on the top.
Under no circumstances freeze it again just to cook it frozen, because it just ruins the texture of the cheese, the sauce gets watery and it's just not a good thing.
If you have leftovers, eat it the next day or two. Remember, all components of the lasagna have been cooked already (unless you made it fresh and used the dry cooked lasagna layers) but a store bought one, most likely has been cooked already.
Now if you have smaller 1 or 3 pound ones, you can put them in the microwave and they will be just fine, and no, a few days defrosted is also okay, and most likely 5 to 15 minutes on high heat, rotating the lasagna will be all right.
It should be safe - a couple days in the fridge is not generally a problem.
I would be tempted to freeze it again before cooking, just so that it's cooked the way the manufacturer expected. At the very least it'll let you use the time on the package, and it's possible it actually matters, because they're expecting something about it staying cold inside for a bit as it bakes.
It's also possible that it'll come out a bit soggy since it's had time to sit and soak while thawed now, but not much you can do about that. Just go for it; worst case, you'll still have lasagna to eat!