Roach infested unit with no window

[Nat C.]

My friend is currently staying with me because her unit is unihabital, yet she's still paying mid full rent. We went to view the property around 10 Feb and the place was utterly trashed as the previous tenant had just been evicted and left it in a disgusting state. The landlord said it would be cleaned and fumigated by 15 Feb move in. I helped my friend move in and it had been cleaned but it was still absolutely disgusting. The fridge was filled with roaches, there was dirt and rice all over the floor, it was really, really bad. 2 of us spent 2 full days cleaning. The roach problem was overwhelming.  The landlord had it sprayed around 17 Feb and there has been very little effect. 

She ended up staying with me as she couldn't move in with the roach infestation. She went to check on the roach situation a week later and found the property had been burgled. They had ripped the window AC unit out and broken the door in and stolen the few possession she had. She informed the landlord immediately. Its now been 1.5 weeks and the window AC hasn't been replaced or boarded up. Now on top of the roach situation, the unit is filled with flies and mosquitoes as it's open to the elements.

Upon my encouragement she called the landlord to ask for a rent reduction for this month, as she has not stayed there one day since she started paying rent. He actually verbally abused her for asking.

The whole situation is rather unpleasant. I don't think she should be paying rent for a unit which has been uninhabitable since day one. Does anyone know the best way to handle this situation?