Extension of tourist visa (Kuala Lumpur)

Hi,

I have a relative who is going to be staying with us for 3,5 months. This making the 90 days granted on arrival not enough. In regular circumstances I would suggest she left a couple of days to Singapore receiving new days upon reentering Malaysia, but in this case this is not a very good option as she suffers from a chronic illness and an extension at a nearby immigration office would be more suitable. So does anyone know is this is possible and if so, how much does it cost?

Kent