Maitland Ward Says Danielle Fishel Might Hate Her Due to 'BMW' Hotness

Maitland Ward has a theory about why things aren't great between Danielle Fishel and her -- and it's all about the former costars having an unspoken war of hotness.

We got the actress -- who's doing adult films lately -- in L.A. on the heels of her releasing a memoir, "Rated X: How Porn Liberated Me from Hollywood." She's dishing juicy stories she's experienced in the biz ... including while shooting "Boy Meets World."

One of the nuggets that seeped out into her writing was an apparent feud that developed between Topanga (Fishel) and her. The puzzling part of that revelation is Maitland tells us the beef evolved out of nowhere ... at least on the surface of things.

We asked why she thinks Danielle might've given her the cold shoulder in recent years ... and what sparked the apparent animosity?

In Maitland's eyes, she thinks it all goes back to the Disney set they used to share, and the spotlight she thinks Danielle wanted all for herself.

Not just that, Maitland also suggests that her pivot into porn might have something to do with this -- she says Danielle's a bit more straight-laced than she is, and her career shift probably doesn't sit too well with her ... especially since Maitland's character was already getting the extra-sexy treatment during their original run way back when.

Speaking of that, there's another sort of bombshell Maitland revealed in her book -- namely that producers for the show allegedly used to ask her to model lingerie as they were tinkering with storylines.

Slimy stuff, no doubt and painfully reminiscent of allegations other child stars have recently made about their on-set experiences.