Descriptive of a sudden and inexplicable aversion to entering a particular shop. This can be caused by any one or combination of the following factors: the apparent attitude of the shop assistants, a shop being far too brightly lit, a shop with hardly anything in it and lots of space, a shop that's entirely white inside which could make you feel a bit scruffy in comparison (especially make-up counters), a shop full of very delicate displays of highly breakable things, shops with mirrors everywhere, quiet shops with too many members of staff standing around who might try to 'help' you...
"When she noticed the stuck-up, hoity-toity looking shop assistants standing around bored, just waiting to instantly judge her then totally ignore her as soon as she entered, she suddenly felt all shop shy and did a complete u-turn in the doorway to the fancy lingerie store. 'I didn't really need any new panties anyway' she thought to herself..."
Too self-conscious to enter a shop for fear of embarassment because it's too 'cool', too bright, or that you may break something.
She went to enter the shop, but suddenly became Shop Shy and performed a u-turn in the brightly flood-lit doorway when she realised all the staff were standing still and staring at her, ready to pownce and ask her lots of questions.