Sandra "Pepa" Denton, 1/2 of Salt-N-Pepa, is still shaken and confused by her encounter with Southwest Airlines this week, when she says she got treated like a criminal without displaying any criminal behavior!!!

It's a perplexing tale, for sure -- but the "Push It" rapper joined "TMZ Live" Wednesday to give us her blow-by-blow account of SW pushing her off a flight Monday headed to Nashville from Las Vegas.

Pepa says she purchased 2 seats to give herself extra space for an injured knee, but wasn't wearing her protective brace when a flight attendant accosted her over the extra seat.

Next thing she knew, a man popped up asking Pepa for her extra seat, claiming he was en route to a funeral -- but she says when she asked him, eye-to-eye, to confirm the funeral story was true ... his lip quivered and he refused to do so. She took that to mean he was lying.

Pepa tells us before she could process that fiasco, a flight attendant ordered her off the flight -- at which point she started recording on her phone -- and she says cops met her in the terminal to escort her outside.

As for why she was booted ... Pepa is confused, telling us she didn't yell at anyone. Independently, we spoke to another passenger -- Shannon McCormack was sitting in the same row and confirmed she never saw Pepa argue at all, until she got the boot.

Shannon says one flight attendant got upset when Pepa said she was going to record, and told her she didn't have "consent" to film. Moments later, she says a different attendant came on board and said, "You, Denton, off!"

Now, Southwest did refund Pepa the $2500 she paid for her 2 seats. The airline tells us police only got involved because once she was refunded, she didn't have a valid ticket, and it's standard for cops to escort unticketed people from the terminal.

Further, the airline, claims it removed her from the flight because she failed to listen to a crew member's instructions. We pressed, but SW would not say what instruction she didn't follow. Pepa and Shannon don't know either, and both point out she left the plane calmly.

Bottom line ... Pepa says Southwest's story isn't gonna fly with her attorneys!!!