Hi Littlelea
Once you reach senior age you should be experienced enough to be able to select music that is appropriate for you but yes, it can be difficult to find the right piece of muisc.
You want to stand out from the crowd at your age so something unique would be good.
There are some great ideas on
youtube - if you search for "Showstoppers" you will get loads of results from an American TV show - its basically like our festivals but on a bigger scale.
The Americans are experimenting with hip-hop styles for dance now, maybe you would like to try that
However, many of the adjudicators in festivals are 'mature' and they prefer to see 'traditional' tap music being used. If you are able to build up a selection of 3 or 4 different solos using different types of music you can use the most appropriate music depending on who the adjudicator is in a festival.
Watch a few sections and try to work out her likes and dislikes and just use the the one you think would suit that particular festival.