There is nothing wrong with single girls wearing makeup as a matter they should be wearing it! Obviously if applied correctly only- if someone is wearing heavy eye makeup or an overly bright lipstick yeah there is something wrong. There is a difference between attractive and attracting.
Now for wearing makeup in general- Everyone should try to look their best regardless if they are single or married. So blush to cover up paleness or eyeliner to bring out your eyes a bit or a nice gloss to your lips…it just enahnces your appearance, and just makes you look more vibrant! Its actually quite annoying when i see other girls or even marrieds (some teachers too) who are walking around with a pale face or dry lips- just put something on!!