I think she should have removed the root. The top is usually not that painful.
If the root is not removed it is going to grow in deeper and deeper causing pressure to the nerves and resulting in pain. The root needs to be removed otherwise the corn will regrow, unfortunately. It is like a corn in humans.
Personally I would apply a Scholl Removal Plaster (or any similar) for a few of days securing it by putting on a boot on the dog's paw. If it causes any side effects I would stop using it. Worthy of trying especially when the top is taken off and it is easier get to the root. One must remember that only the corn should be under action of the medicated pad. It is easy to find any of the products on the Internet (it may be also a liquid or cream with very precise applicators).
Archie had a corn removed under anaesthetic a couple of months ago and while he was under had his teeth cleaned and a wee lump removed-talk about an mot! however it seems to have worked altho it took a while for the tragic limp to disappear might just have been our Archie