Someone can definitely be addicted to lipgloss. The effect of the touch and feel it brings to your lips can absolutely become an obsession. There is nothing like a glossy, shiny lip.
im not sure about lip gloss but im pretty sure you can be addicted to chap stick. i heard somewhere that the makers of chap stick put something in thats addictive and causes you not to be able to go without it. i believe it might be true because i cannot live without it.
It's not an addiction, exactly but your lips can become accustomed to lip gloss and you can start to feel like you need it. You can break the habit but in the mean time you will experience really dry, sometimes itchy lips. There's nothing really wrong with wearing lip gloss all the time though if you like it.
Lipgloss itself is not addictive. Your friend probably just became accustomed to repeatedly swiping gloss on and likes the hydration and the look it provides.