If I was hit by a car as a pedestrian, how do I know how much to ask for in a settlement offered by her insurer?

You should not settle the case until you complete your medical treatment and are released by the doctor or are declared by the doctor to be permanent and stationary which means having reached a point in your medical treatment where no further improvement is anticipated.  When you complete your medical treatment and are released by the doctor or are declared to be permanent and stationary, obtain your medical bills, medical reports and documentation of any wage loss.  Your personal injury claim filed with the at-fault party's insurance carrier should include these items.  Compensation for the medical bills is straight reimbursement.  Compensation for wage loss is straight reimbursement.  The medical reports will document the nature and extent of your injuries and will be used to determine compensation for pain and suffering which is an amount in addition to the medical bills.

There isn't any mathematical formula for determining compensation for pain and suffering.  It depends on the facts such as whether or not you are having residual complaints which would mean additional compensation compared to someone who has fully recovered.  If the medical reports indicate that you will need future treatment, an estimate of the cost of the future treatment discounted to present value should be included in your compensation.  I would normally ask for quadruple the medical bills to compensate for pain and suffering but NOT expecting to get that.  This would be a starting point in negotiations and the insurance company will respond with a lower offer.  Continue negotiating to try to get the insurance company to increase its settlement offer.  If you are dissatisfied with settlement offers from the insurance company, reject the settlement offers and file a lawsuit for negligence against the at-fault party.  If the case is settled with the insurance carrier, NO lawsuit is filed.  If the case is NOT settled with the insurance carrier, you will need to file your lawsuit for negligence against the at-fault party prior to the expiration of the applicable statute of limitations or you will lose your rights forever in the matter.

You don't want to settle until you have completed your medical treatment and are released by the doctor or are declared by the doctor to be permanent and stationary because prior to that you wouldn't know the total medical bills, total wage loss and wouldn't have the final medical report on which to determine compensation for pain and suffering.  Once you settle with the insurance company, you can't go back later and ask for more money.  The one thousand being offered is too low.