"Pippi Longstocking" actress Tami Erin has an ex-boyfriend who should worry about getting shot ... this according to her own father.

David Young -- Erin's ex live-in BF -- ran to court a few days ago for an order prohibiting Tami from coming near him. David says he broke up with Tami nearly 2 years ago and she went radio silent ... until last month.

David says Erin started calling him at his Merrill Lynch office and leaving threatening messages. He didn't think much of it, until he spoke with Mr. Longstocking, who told him his daughter was "very dangerous" and he had reason to believe she had a gun.