dark shadow on upper lip (female)

Are you naturally dark? If so, then it's probably tiny tiny hair that you can't see. If that's the case, I definitely suggest facial hair bleach - you can buy it from most major chemists; boots

I really don't think it's from "tiny hairs". If it's a dark shadow then it's most likely melasma (which is a pigmentation of the skin). It's actually quite common in women aged 20-40, and is also common on the upper lip region. It's literally just pigmented skin, and is generally aggravated by the sun. You should make sure you wear suncreen whenever you set foot out of the house - this will tackle the cause of the problem so it should eventually go away over time. If you want to get rid of it fast, you can use a skin lightening cream. (Most skin lighteners don't actually "bleach" the skin - this is a common misconception - they just block the skin from becoming pigmented.) Try Fashion Fair Vantex cream.

Hope that helps.