K.A.
When my son had a leg cast they told us to use a hair dryer. When that wasn't working they had us come in. He kept getting really bad rashes underneath his cast. He was on antibiotics because of the rashes in case it was MRSA because it was pretty bad. Testing reviled it wasn't but while waiting for results they wanted to be proactive. They had to remove the cast and replace it once and by the third time it had healed enough that they put him in a walking boot instead. If a hair dryer isn't helping and it's really bothering her I would bring her in. They may need to recast it or change it out.