gf smells and tastes bad.

my gf (18) of 2 years wants me to eat her out and pleasure them more but i find it gross. they don’t drink water ever, just soda and they eat unhealthily and i think it’s having an affect on their taste and smell? i don’t want to bring it up to her as it would embarrass her but i also don’t want to pleasure her when it smells and tastes bad. she eats me out and pleasures me just fine and just wants it reciprocated. what do i do? how can i bring any of this up?