If the item is a gift, then it belongs to you and you can sell it, keep it, or throw it away, without fearing that the original owner will change her mind and return to demand the items. Legally, an item is considered a "gift" if 1) there was actual delivery of the item, 2) the donor had the intent to give the item to you as a gift, and 3) you accepted the gift.
It sounds like your former friend delivered the washer and dryer, with intent to give it to you as a gift, and you accepted the washer and dryer. In my opinion, the washer and dryer are a gift. They belong to you now and you can do whatever you want with them.
If your former friend told you she only wanted to store the items at your house for a while, or if she declared her intent to give the items to you but the items remained at her home, then it's not a gift. If she sues you, she won't win unless she can prove that you coerced her into delivering the washer and dryer to you, or that you knew she never intended to give you the items and only meant to store them at your house for a while.