10 month old cairn terrier pees on floor when she is upset

[leeah]

Hi,

My 10 month cairn terrier has potty trained. She usually pees on the newspaper on shoe tray (her toilet).

in past two weeks, her pee appear next to her toilet. I thought it could be accident. this problem seems occuring more frequently.

it seems she is upset about something.. I am not sure.

How can I stop her from peeing on floor but her toilet.

thanks
Alic