Tell her that while the stereo was on she had a phone call but you couldnt make out who it was, if shes a "natterer" shee desperatley ring all her mates for at least 30 minutes trying to find out who it was, if shes got a boyfirend (?) then make out it was him shell go frantic trying to ring him. Either way to make a call she needs to turn down the volume

Once shes out of room take the lead out of the back of the speaker, place sticky substance on lead and replace making sure theres no electrical contact and
voila looks like the speakers plugged in btu its not - it doesnt work and when ur mum comes home tell her the stereo doesnt work and that your sis was using it last
