Kyle & Kim Richards -- Relationship May Be Beyond Repair

Kyle and Kim Richards are sisters at war ... and it's way more personal than just a vicious dog attack.

There has been radio silence between the two -- with the exception of a brief encounter after a "Real Housewives of Beverly Hills" reunion show -- since Kim's dog attacked Kyle's daughter in November.

We're told Kyle is furious Kim hasn't 86'd her pit bull -- which has a long rap sheet and tore into 18-year-old Alexia's hand.

But it goes deeper than puncture marks. Kim feels betrayed by her sis because she feels fellow housewife Brandi Glanville has been more attentive to her struggles with substance abuse than Kyle.

What galls Kyle is that she feels Kim is an ingrate ... Kyle says she and Mauricio have been a driving force all along in trying to keep Kim sober, and she feels Kim is using them as scapegoats to deflect responsibility for her addiction problems.

Our "Housewives" sources say nothing is permanent, but they give a reconciliation little hope.