HELP, What can I do to lessen my cats loneliness during the day,she attacks me when I get home?

I have had my cat for 2 months now. I am out of the house 12 hours a day (work). She has been fine with this until a couple of days ago. She becomes hostile when I get home--bites and scratches me and runs around like she is on catnip. For now, I can not get another cat. Is there anything I can do to help her feel less alone during the day? Should I leave a radio on? I look mauled...my arms and legs are all scratched up. She acts incredibly angry at me. I don't get why this is happening now since I have had her since April? Please Please provide some suggestions