Does the word "altitude" refer to the character's height? Is it a common expression?
Native speaker’s answer
"Altitude" actually refers to height or elevation, i.e. the height of something in relation to the ground or sea level. In this case, the speaker is making a joke that the length of the high heels her friend is wearing may be affecting her judgement, due to the decreased oxygen level one finds at high altitudes. Ex: The plane is flying at an altitude of 35, 000 feet above sea level. Ex: Oxygen levels decrease at high altitudes, so mountain climbers often carry oxygen tanks with them.