The bottled Crystal Light is sweetened with Splenda, so if she's drinking that it's not as bad for her.

I was the same way until I just started keeping the fridge at work stocked with bottled water. Since it was always there I would just drink the water instead of buying a soda from the vending machine.

Now I drink a huge bottle of water (64 oz) just about every day at work. Other that the frequent trips to the bathroom I think I feel much better than drinking diet soda like I was before.

I still have an occasional diet soda in the evening, but I try to make it a treat instead of a staple.

She might want to try unsweetened kool aid and sweeten it with splenda as an alternative to the powdered Crystal light. Plus kool aid is much cheaper.