Generally the issue with electronics is more going out of the US so South America where high duty / import fees drive up prices. In these cases you will see careful screening of people with numerous items [I've heard Brazillians argue that the 3 brand new laptops they had came with them for studying] however I believe Panama is an exception to the duty issue and thus would, if anything, inverse the issue.

Unless your girlfriend's mother travels with a lot of electronics [i.e. multiple laptops, cameras, phones, etc] it's unlikely customs will pay much, if any, attention to the gadgets she brings through. There are those oddball people who use the original box for storage, that would clearly be a bad idea but a couple items in your baggage is far too common to check.

Of course if she does buy anything while out of the country it should be declared. The fines far outweigh the small duty paid coming back to the US, and that doesn't just go for electronics either... clothing, liquor, it's all fair game.