Landlord tenant statues typically state that a landlord must provide a rental unit with electrical, plumbing, heating and ventilation in working order. It's not unusual that air conditioning might not be included in this statute. Attached is the statute for Indiana that implies if air conditioning is included in the lease it must be in working order:
No statute that includes air conditioning specifically states this must be central air. She could..and should...provide an adequate source even if these are window units.
It's doubtful you can "make" her do this if she refuses. At best you could request that the lease be terminated if she does not provide you with this.
One word of warning. Be careful about playing the "mold" card. It has, unfortunately, been terribly overused by tenants who either are unnecessarily worried that every evidence of mildew is deadly mold or who believe that mold is an instant legal out for them. It's not.
However, if there is mold on, say, a wall then this may be evidence there is leak between the walls and this needs to be looked into.
Gail