All proceeds from the single will be going towards Wiltshire Air Ambulance in Hannah's name. Since Hannah's death 18 months ago, £78,000 has been raised in her memory.
Talking about her single, Emily, said: "I have always been into music, and I have always used it as a way to cope with anything, so with her passing I would play music often.
"To sing my own song has helped me come to terms with it.
"I take GCSE music and my teacher gave me a few chords to work with, I went home and started playing around with them and the song kind of happened.
"Hannah is my best friend, I hung out with her every day at school.
"It is quite overwhelming having so many positive comments about it. It makes me feel a lot better about myself and it is nice to have the support of other people.
The putting together of the single was a community effort, with local record label Supermarine Musc volunteering their time and expertise to produce the song after seeing a video shared on Facebook by Emily's mum, and Rupert Barker taking photo's and shooting video.
Hannah's father, Andy, was also asked to play guitar on the track and he was very honoured to do so.
He said: "The song is a very nice gesture and the local interest gathered to the point Supermarine Music invited Emily in to record.
"I was asked how do you fancy playing the guitar and to be asked to be part of it was very touching.
"A couple of days after Hannah died, I was wondering how I was going to get myself through this and there was a dusty old guitar in the corner I hadn't touched in three decades.
"I plinked away for at least an hour, and that to me became a coping strategy as I became more interested in the guitar.
"We all at some time in our lives suffer loss in that respect, this music will really affect anyone who listens to it.
"Two days after Hannah died, my wife and I decided to start fundraising for Wiltshire Air Ambulance.
"We had an initial target of £1,000 thinking we would reach it in a few weeks but we reached that in about 15 minutes.
"18 months on we have raised £78,000 and 30 rescue missions have been funded in my daughter's name.
"It would be so lovely if we could get to £100,000.
To download the track is a minimum £1 donation and Emily hopes to raise £500.
To download Sky tonight, please visit: www.musicglue.com/emjones.