Hell hath no fury like a best friend scorned!

Heather Locklear still hates her former BFF Denise Richards so much that she fired her daughter Ava’s longtime nanny — because the woman refused to kick Denise’s kids out of a preschool she owns, sources say.

The nanny, Robin Hasen, had been “like a second mom” to 9-year-old Ava, insiders say. But when Robin wouldn’t kowtow to Heather’s demand to boot Denise’s girls, Heather let her go.

“Denise and Heather’s ex-hubby Richie Sambora may have split up, but that doesn’t mean Heather’s ready to bury the hatchet,” said an insider.

“Heather is still mad as hell at Denise. She believes Denise lied to her when she ran off with Richie just as he and Heather split up.”

The feud between Melrose Place sexpot Heather, 45, and 36-year-old Denise has been boiling ever since Denise started dating Bon Jovi guitarist Richie, 47, early last year.

And nanny Robin is the latest victim caught in the cross-fire.

During the seven and a half years she worked as Ava’s nanny, Robin was like a member of the family, the insider revealed.

“Robin did everything for Ava — and Heather came to love Robin just as much as Ava did,” the insider divulged.

When Robin opened the Cornerstone Pre-School two years ago in Agoura Hills, Calif., Denise immediately enrolled her daughter Sam, now 3. Later, she enrolled her younger daughter Lola, 2.

But after Denise and Richie got together, “Heather repeatedly put pressure on Robin to kick Denise’s girls out of the school,” said the insider.

“When Robin refused, Heather fired her. It came as a terrible shock to Ava — and Richie wasn’t happy about it either. But Heather refused to bend.”