imagine herself as a ballerina

No- the second part of the sentence is confusing- although I think that people can ascertain the meaning the way it's written, I would rewrite it thus:

When the ballerina programme ended, Jane put on some music and began to imagine herself a ballerina, dancing as it she and the music were one.

or you could make your meaning even clearer by saying:
When the ballerina programme ended, Jane put on some music and imagining herself a ballerina, danced as if she felt as one with the music.

There are all sorts of ways to express it- you just have to choose the one that sounds the best to your own ear - especially with a subject such as this - flow is important.

I am afraid Aidan is mistaken, Tanguatlay. I think he has misunderstood your question. Your sentence has a slight fault, namely that we usually talk or write about ballet programmes, not "ballerina" programmes. With that amendment, it...

When the ballet programme ended, Jane put on some music and began to imagine herself as a ballerina and danced as though she were one (i.e. a ballerina).

... is absolutely fine, perfectly grammatical, and elegantly avoids repeating the word "ballerina". Good use of the subjunctive also.

Well done.

It is not confusing at all to a native speaker.

You're right contrex - I did misread it.
sorry Tanguatlay.

I must say, Aidan, that the idea of the girl dancing as if she were "one with the music" is a very pretty one.

Yes, well - that's how music affects me. I was reading it as if I were that little ballerina.
As a matter of fact, I did used to dance in the hallway outside my brother's bedroom where he was playing his music (which I liked) but he wouldn't let me actually open the door and enter the room, so I would just spin and twirl in the dark - all by myself.
I was a weird, spacey kid in some ways.

Funny - someone on another thread was just talking about creating one's own subtext and how one shouldn't do that - I do it all the time- and I did it here.

Many thanks to your help, Aidan and Contrex.

I do it all the time too.