they don't necessarily do so well in higher temps. and they need well drained soil.
what
zone is she in?
if she really wants to grow them, she should do new
plants when the temps are going to be a bit lower - during the winter months if she's in s. florida - so that they have time to get well established before the higher temps set in.
she should also start them inside and not transplant to outside until the tap root is pretty well established. i don't know how long that takes - she could just gently move the soil in the pot to take a look at the root to see how big it is.
once a good-sized taproot is established and she's transplanted them outside and they get established there, she should have a good (and continuing supply). they should be fertilized every few weeks.
dandelions are a vegetable and they are chock full of vitamins A, C and niacin.