The former 'Real Housewives of New York' star shared several sweet pics focused on her mom, Bernadette, who she says passed away from lung cancer ... before diving in and truly breaking down her complicated feelings for her mother.

It's a pretty long analysis ... but, BF sums it up well at the top -- saying her mom dealt with her demons while adding Bernadette made it so Bethenny needed to flee an abusive home early on.

Bethenny calls her mom funny, cultured and wise ... before saying she simply wasn't equipped to be a mother and didn't enjoy the responsibility all that much.

In fact, Bethenny says she only began mending fences with her mother after her daughter Bryn, now 13, consistently pushed to meet her grandmother ... and acknowledges she's grateful they did have time to work on their relationship.

Frankel ends on a positive note ... saying she considers her mother family despite all they've gone through and encouraging others to reach out to their own estranged friends and fam.

Anyone who's followed Bethenny's career knows how she felt about her mom. She opened up about their relationship in a 2010 People cover story ... saying "There was a lot of destruction: alcohol abuse, eating disorders and violent fights."

It seems Bethenny's putting much of that aside now that her mom's gone ... while not sugarcoating their relationship one big.

Bernadette was reportedly 73.