HOLD IT !!!!!!!! Now if you're talking to a Lebanese (and maybe Palestinian) that would mean exactly the opposite, unlike Egyptians or Syrians we use ma for "don't" so "ma tistihe" means "Don't be shy", and if you're talking about someone else who's shameless or rude it becomes: ma btistihe (she doesn't get shy, or in another context she's shameless)

Depends on circumstances/tone, can be any of the following: 1) Don't be shy, just do whatever you supposed to do. 2) Be shy, you've done something awful.

It means, "you are shameless".

"ma"(arb) is the same as "la"(arb) = both used for negation. tistehi = to be ashamed /shy. ma tistehi = (you're/she's/..etc) shameless .

be shy