Britney's younger sister appeared Wednesday on "Good Morning America" ... hawking her book, "Things I Should Have Said," about her family. Jamie Lynn said she's happy the conservatorship ended, but bobbed and weaved when it came to how she felt about the conservatorship during the 13 years it was in place.

She said when the conservatorship was first put in place she didn't understand it and was dealing with other issues ... specifically, she was 17 and having a baby.

But, she said she understands as little about the conservatorship now as she did when it fired up ... which is odd since the saga lasted so long. She says she took no part in the conservatorship during its entire run.

From her vantage point, she says she was helping Britney, and, according to her, the help was welcomed. She says Britney asked her to make sure her 2 boys got what they needed.

One thing she addressed squarely ... Britney's comment to the court that everyone in their family -- including Jamie Lynn -- profited off Britney during the conservatorship. Jamie Lynn says she did not, but then offered that there may have been a "misunderstanding." Britney has gone after Jamie Lynn for remixing some of her songs, but she says it was meant as a tribute, not a money move.

She says she's happy the conservatorship is over because it caused so much family discord.

As for Britney, well she intimated in a post Tuesday night ... 2 can play that game, as in writing a book.