Her third cycle is 25 days long. There are only four to six tablespoonfuls of blood in the whole flow. This is a small amount. The rest is bits of the unused lining and other fluids. By the time your period ends, it will have amounted to between half a cup and a full cup of liquid.
Most women use either sanitary pads or tampons to absorb the flow.
You can buy them in drugstores or supermarkets. Usually they come in packages of ten or more. Every package has instructions in it. They come in different sizes and varieties. Some are for lighter flows.