Ela, if she's placid, could they just gently cut some of the fur away with scissors? or are they thinking they'll need to sedate her and shave? With fur as matted as that its likely its falling away from the skin anyway and they would be able to see where mats meet skin, so with careful snipping its possible, although takes longer.
This makes me so angry,like everyone else has said, I've seen some bad ones in my time, admittedly the worst one was owned by someone who'd had a mental breakdown and just couldnt cope with anything anymore, never mind a longhaired cat's coat. But, the ones with no excuse......well, I just bite my tongque and get on with the work in hand. Some are ashamed, many are in denial and still expect you to believe that they comb the cat everyday!