All insurance companies require that you have an insurable interest in the individual that you are insuring. For this reason, buying insurance on your girlfriend is generally prohibited, but may be acceptable in certain circumstances.
Life insurance companies will not allow you to buy life insurance on an individual in cases where you have no personal interest in that individual's well-being. The person's death must represent a clear financial loss for you.
You must be able to show the life insurance company that you and your girlfriend have been together for a significant amount of time. Several years may be required before the insurance company accepts the idea that you have an insurable interest in your girlfriend. The insurance company may also ask extensive questions about whether you intend to get married or why you wish to purchase life insurance on your girlfriend.
You may want to get married if you are serious about your girlfriend. You must also consider any potential drawbacks to purchasing a life insurance policy on your girlfriend. If you buy a life insurance policy on her and then break up, it won't make any sense for you to have a policy on your girlfriend's life.