Welcome Marty!
There's plenty of knowledge around here and some helpful characters to go with it. My personal recommendation would be to learn how music is structured. Majority of music is written in a 4/4 time signature, which means 4 beats over 1 bar. It's the most common time signature to write in, especially for pop music and dance music. songs are usually structured in bars of 8 and 16. It all sounds a bit complicated but it's quite easy.
Have a look at this video to get started. It's about song writing but this structure will help your daughter understand how music is written and, when it comes to mixing, when to transition from one song to another. If she's into dance music, it's quite similar but most DJ's will have extended versions of their intros and outros which are usually 16 - 32 bars long at either end. Once she starts listening out for this structure she'll pick it up across all forms of music.
Any questions don't hesitate to ask