Hi and welcome to the forum.
The hedgehog being out during the day rings alarm bells with me. It may be because she is actually very hungry. It isn’t normal behaviour for a hog. I have a hedgehog here too which isn’t hibernating and turns up in minus 0 temperatures (although the recent snow has been a bit too much for him). But he never turns up during daylight and neither did the one who was here last year, all winter. It is not necessary for them to do that with the nights so long.
If it is so, that the hedgehog is very hungry, it is very important that you try to prevent it from eating mealworms and instead provide plenty of cat food or good quality hedgehog food. They love mealworms and will fill themselves up with them in preference to anything else if they get the chance – a bit like humans and crisps. But they have very little nutritional value as well as a bad balance of phosphorous to calcium. This can lead to calcium being leached from the bones causing something similar to osteoporosis. It is also very important to provide water. Hard, I know in freezing weather, but if there is a sheltered place you can put it that might help.
If I were you, I would leave cat food out during the day as well. Try to keep the bird food away from where the hog feeds and hope that it eats some of the more nutritious food. It should gradually revert to visiting at night as it should do. (it is important to realise that there is very little wild food around when the weather is very cold). You could also try to catch the hog and weigh it. If it weighs less than 450g. it might need help from a local rehabilitator. You can find your nearest one by ringing the BHPS on 01584 890801. You can also ring your local rehabilitator for further advice. If you have to take the hog to a rehabilitator, make sure that you can have it back for release where it came from once it (hopefully) has recovered.
Good luck
