I wouldn't milk her, it will just encourage her to keep producing milk , which will prolong the problem. Do you have any poorer grass she can go on? Or if you are really worried, somewhere indoors, but still with plenty of room to move about, where she could just have hay or good straw? It is normal for them to be bigger, even though the lambs haven't been suckling much, she is still used to producing that much milk and it's going nowhere - it should just be reabsorbed, and I'm sure she will be fine, just keep an eye for any lumps/heat/swelling.