my mother-in-law is having problems with her 26' travel trailers rear tires wearing. Left tire is wearing on the outside edge and the right tire is wearing on the inside edge. To me this sounds like a axle alignment problem but could it be as simple as tire inflation? Any help would be great Thank you

You certainly want to check tire pressure, but I'd jack up the trailer by the frame and see if the spring shackles and hangers are worn on the right side.