Yes, they are allowed to do this when the lease comes up for renewal. (They cannot make this change or interpose this requirement during the term of a still-in-effect or unexpired lease.) It may be greedy and immoral, but it is legal: there is no inherent right to select your own insurer, and a landlord (or the property manager on the landlord's behalf) is not only free to specify that tenants must have insurance, but also to specificy the parameters of the policy and where and from whom it must be purchased: tenants must decide if they are willing to comply with that requirement of if they will not renew the lease or rent here. A tenant who does not want to rent under those conditions can look for a rental unit from someeone else.