Rachel Summers is the daughter of the Cyclops and Jean Grey of an alternate future. By the time she journeyed to the 616 reality, Jean had been replaced by the Phoenix, so neither of them are really her mother: but that doesn't stop them from acting like it!
We were originally just going to have Marvel Girl hanging in the normal Phoenix Effect display base, but adding the fire effect to it really spiced things up!
And see, they use it to dry their hair because it's made of fire, fire equals heat, and heat equals evaporation. Plus, only one of them can use it at a time, because it's not like the Phoenix can be split into multiple parts and used by several hosts at once, right? Right!
Jean: Stop hogging the hair dryer, Rachel!
Phoenix: Other people are waiting to use it, you know.
Rachel: God, Moms, get off my case!
Phoenix: You don't even have that much hair!