Can my sister get cheaper car insurance through a military discount I may qualify for?

There are a few insurers that offer military discounts — they are typically the same as an employment discount with most companies. But the only way your sister would be eligible to be added to your policy is if she lives in the same house as you. Typically, it is going to be better to keep your policies separate. She can take a look at completing a defensive driving course or bundling in a renters or homeowners policy to get additional savings.