Janine Detore tells TMZ ... her landlord covered the larger-than-life tribute to Ang that had been on the side of her store -- Country Mouse Boutique -- following a dispute over some unpaid bills.

Janine says the turmoil started in September when she underwent tests for some health issues ... and doctors ended up telling her she has severe allergies to mold.

She says the docs suggested checking her store for mold to see if anything in the building was making her sick ... so, earlier this month, she paid someone to do just that.

Janine says she gave her landlord a heads up and got a text back, saying, "Just to let you know, this is coming down" -- referring to the mural.

We're told tensions escalated ... especially 'cause Janine admits she owes $27,000 in back rent. She's convinced the mural cover-up, which Janine says left her granddaughter in tears, was retaliation.

Janine tells us she's committed to finding a new location for the mural ... remaining adamant the city deserves another one, 'cause Ang did a lot for Staten Island.

We spoke to the landlord, who told TMZ a different story ... saying he tried to fix a broken boiler at the store last month, but she wouldn't let his contractors inside. He says when he told Janine she could fix it, and he'd reimburse her, she refused.

The landlord claims she's taking advantage of him and not paying her rent -- adding he thinks she's using the mural cover-up as a publicity stunt.