Don't lower the 250, it'll mess with the ergonomics. Instead, buy a used seat and shave the foam in it. My ex-gf was also 5'3" at about 120lbs and she did that. It allowed her to stand with both feet on the ground, on the balls of her feet. Practice the left cheek sneak until you're comfortable stopped with only 1 foot flat on the ground, then put the original seat back on.