'Dance Moms' Star Sues -- Abby Lee Miller is a 300 lb. Beast Who Trie -

Abby Lee Miller is a huge and vicious bully who attacked one of her "Dance Moms" co-stars like a rabid dog ... this according to a new lawsuit filed by the alleged victim who's looking for at least $5 million.

Kelly Hyland just filed a lawsuit against Abby over the knock-down drag-out catfight TMZ first reported last month ... where the two women came to blows during a rehearsal in NYC.

In the suit ... Hyland, a regular on the show, claims she got fed up with Abby yelling at her 2 daughters -- but when she attempted to leave ... Abby jumped in front of her and started yelling and lunging toward her.

Hyland goes on to describe a Cujo-like attack ... claiming, in the docs, Abby was "gnashing her teeth loudly attempting to bite [me]."

Then she added this gem ... "Miller is a very large woman" who she believes "weighs around 300 pounds or so."

In the docs, Kelly says she slapped Abby and pulled her head away, but only in self-defense. The brawl aired -- pretty much how Kelly describes it -- this week on Lifetime.

Kelly also claims producers intentionally drove her away from the fight and put her on a plane -- knowing police would issue a warrant for her arrest ... and thereby create a juicy story line.

Hyland is suing Abby and the "Dance Moms" producers for assault, defamation, and breach of contract -- she claims she hasn't been getting paid regularly since the fight. She also wants $5 mil in punitive damages.