Headphone for elect. Guitar....suggestions please...

Hi.
My young daughter got her electric guitar and now she's turning into a little Jimmy Hendrix...well many not yet that good… but she does make noise....

What should I get her? I seed something cheap and good enough...

Also I read about the Sennheiser PX100, good reviews and cheap...
Would it be a good choice for listening to an electric guitar and all the fuzz of that kind of music?
I know that the headset jack won't be the right size, so another very important question for me is , can I buy an adapter for this smaller jack, so it fits into a standard Guitar ampli jack ( I don't even know the size , do you know? ) anything I shoud be carefull about?

Thanks for your time

Stef, Montreal, Canada