Yes, bed-wetting can be related to sickle cell disease. The kidney is damaged by sickling from early in childhood, and cannot hold onto fluids normally. The kidney produces urine through the night, more than for a normal child, and the urinary bladder fills up during the night. Then the child has to urinate, either waking up to go to the bathroom or urinates while still asleep. Medications that help other children with bed-wetting usually do not help those with sickle cell disease. Usually, the solution is to persuade the child and train the child to wake up during the night (reward system, calendar of "dry nights," having the child wash the sheets, setting alarm clocks, using alarm devices that awaken the child when the underwear is a little wet, having nightlights between the bedroom & the bathroom). Cutting back on drinking fluids for a couple hours before bedtime and going to the bathroom before going to sleep are also helpful.

Median survival of individuals of all ages with sickle cell disease based on genotype and sex (Platt OS, Brambilla DJ, Rosse WF, et al. Mortality in sickle cell disease- Life expectancy and risk factors for early death. N Engl J Med 330(23): 1639-1644 (1994). 

Sex and Genotype Median Survival
Males with Hb SS  - 42 years
Females with Hb SS - 48 years
Males with Hb SC - 60 years
Females with Hb SC - 68 years

Note that this was reported in 1994. Now in 2002 many new advances with the medication hydrea, the new pneumoccocal vaccine Prevnar, stroke prevention with TCD, and cures with bone marrow transplants the life expectancy is increasing.

Many women with sickle cell disease experience pain around the time of their menstrual periods. Female hormone changes probably affect the way sickle cells and blood vessels interact. The use of ibuprofen at the very onset of the periods is a good idea, but needs to continue around the clock for the duration of the period (600 mg every 6 hours) in order to maintain an effect on reducing inflammation. 
Alternative medications include Naprosyn, another member of the non-steroidal 
anti-inflammatory drug type. This approach may not completely prevent the pain 
episode, so a stronger pain medicine like Tylenol with Codeine should be begun as soon as she is having moderate or worse pain, to try to keep the symptoms from getting too severe. Lastly, for women who have this problem every single month, we have some success with hormone treatments to try to keep the estrogen and progesterone in the body from going to extremes. This would involve the medications usually used for birth control - the oral contraceptive pills or injectable Depo-Provera. Some parents naturally get a little nervous about this approach in their teenaged daughters because of the fear that it gives the child "license" to have sex. This is something that you will need to discuss with your daughter and her primary provider to see if it is an acceptable treatment. Most of the women (young and older) whom we have treated with hormone therapy report a reduction in the pain episodes associated with their periods.

If food is taken in moderation and with a generally balanced selection of foods, I cannot think of many foodstuffs that would be hazardous to somebody with sickle cell disease.
Possible harm from excess iron if somebody already has iron overload from multiple transfusions - so there is generally no need for iron supplements in sickle cell disease. Possible harm from too much diuretic effect if excess caffeine or alcohol is taken, because the fluid lost will make dehydration more likely and more tendency for red blood cells to sickle. Be cautious with medications that tend to dehydrate the body, lower the oxygenation or slow the circulation or enhance clotting.