She is giving you great advice! Here is a bit more..Many ordinary factors can upset the balance of fluid in the body to cause what is called "edema".
Some of the causes are
Immobility. The leg muscles normally contract and compress blood vessels to promote blood flow with walking or running. When these muscles are not used, blood can collect in the veins, making it difficult for fluid to move from tissues back into the vessels.
Heat. Warm temperatures cause the blood vessels to expand, making it easier for fluid to cross into surrounding tissues. High humidity also aggravates this situation.
Medications. Certain drugs, such as steroids, hormone replacements, nonsteroidal anti-inflammatory drugs (NSAIDs), and some blood pressure medications may affect how fast fluid leaves blood vessels.
Intake of salty foods. The body needs a constant concentration of salt in its tissues. When excess salt is taken in, the body dilutes it by retaining fluid.
Menstruation and pregnancy. The changing levels of hormones affect the rate at which fluid enters and leaves the tissues.
Most likely I have hit on something that may ring a bell to you. Most likely it is not medical. If it is a condition may be:
Heart failure. When the heart is unable to maintain adequate blood flow throughout the circulatory system, the excess fluid pressure within the blood vessels can cause shifts into the interstitial spaces. Left-sided heart failure can cause pulmonary edema, as fluid shifts into the lungs. The patient may develop rapid, shallow respirations, shortness of breath, and a cough. Right-sided heart failure can cause pitting edema, a swelling in the tissue under the skin of the lower legs and feet. Pressing this tissue with a finger tip leads to a noticeable momentary indentation.
Kidney disease. The decrease in sodium and water excretion can result in fluid retention and overload.
Thyroid or liver disease. These conditions can change the concentration of protein in the blood, affecting fluid movement in and out of the tissues. In advanced liver disease, the liver is enlarged and fluid may build-up in the abdomen.
Malnutrition. Protein levels are decreased in the blood, and in an effort to maintain a balance of concentrations, fluid shifts out of the vessels and causes edema in tissue spaces.
Symptoms vary depending on the cause of edema. In general, weight gain, puffy eyelids, and swelling of the legs may occur as a result of excess fluid volume. Pulse rate and blood pressure may be elevated. Hand and neck veins may be observed as fuller.
So that said, what about treatment? It is based on the cause. Simple steps to lessen fluid build-up may include:
Reducing sodium intake. A high sodium level causes or aggravates fluid retention.
Maintaining proper weight. Being overweight slows body fluid circulation and puts extra pressure on the veins.
Exercise. Regular exercise stimulates circulation.
Elevation of the legs. Placing the legs at least 12 in (30.5 cm) above the level of the heart for 10-15 minutes, three to four times a day, stimulates excess fluid re-entry into the circulatory system.
Use of support stocking. Elastic stockings, available at most medical supply or drug stores, will compress the leg vessels, promoting circulation and decreasing pooling of fluid due to gravity.
Massage. Massaging the body part can help to stimulate the release of excess fluids, but should be avoided if the patient has blood clots in the veins.
Travel breaks. Sitting for long periods will increase swelling in the feet and ankles. Standing and/or walking at least every hour or two will help stimulate blood flow.
ANd of course WATER WATER AND MORE WATER!!!! Just as Viethulk4 suggested. A half gallon is recommended for the average individual by the FDA but also 5-10 ounces every 15 to 20 minutes of working out.
Alternative treatment
Dietary changes, in addition to cutting back the amount of sodium eaten, may also help reduce edema. Foods that worsen edema, such as alcohol, caffeine, sugar, dairy products, soy sauce, animal protein, chocolate, olives, and pickles, should be avoided. Diuretic herbs can also help relieve edema. One of the best herbs for this purpose is dandelion (Taraxacum mongolicum), since, in addition to its diuretic action, it is a rich source of potassium. (Diuretics flush potassium from the body and it must be replaced to avoid potassium deficiency.) Hydrotherapy using daily contrast applications of hot and cold (either compresses or immersion) may also be helpful. | 
