I have just backed up my iphone on my laptop for the first time in a while and updated my handset. After I finished, I then realised that I was logged into my friends iTunes account on my laptop. Does this mean that my friend will have access to everything that is on my iphone when they log into their iTunes? texts / contacts / emails etc? I am worried that all of my information including text messages has now been uploaded to their handset and I don't want this to happen. I want to make sure that when they back up their phone, they won't be uploading my information from their home computer to their phone. Can someone please tell me that the back up is just on my lap top and not on their overall iTunes???
iCloud and iTunes backups are totally separate. If you backed up to your computer, it doesn't matter whose account was logged in on iTunes. The backup is on your laptop.
iCloud backups occur directly from the device and who is logged into the device does matter in that case.
Also I think you are misunderstanding what happens during a backup. Nothing is transferred to the phone. What you are describing would be a restore.