The blisters could be from a few different things, scratching, her face rubbing on blankets when she sleeps, even the skin to skin contact when breast feeding can cause blisters. There isn't a whole lot you can do except try to be aware of it and avoid it if possible. I definently do not agree with your dermatologist saying to put vaseline over and open wound, it doesn't let it breath and has no antibacterial properties to it. If they are just occasional blisters you might want to try putting neosporin on them instead. This should go away by itself, and may come right back again as soon as it heals, especially if it is an area that has alot of movement involved. Scratching or stretching areas of the skin is a frequent cause of blisters which can heal on their own and then the skin appears to peel off in patches where the blister was. Sometimes you may never know she had a blister until it dries and peels later. Keep her comfortable and make sure none of these become infected and things should be ok.