Thin Lips and Dark Skin

[MissPanther]

I've been making a portfolio with my friends as models, and I have a Sri Lankan friend with beautiful large eyes, but thinner lips.

I have NOT tried to go over the boundaries of her lips to make them look fuller, but I have been given mixed advice on this (Yes do it, no don't do it). My question is, what should I do to make extremely thin lips look fuller besides a sparkly gloss?
I was thinking of doing two tones of lip stick to give more definition and depth to the lips

 

[she]

my sister is dark skinned and has virtually no top lip and it's hilarious to see her draw her little line above the middle of her natural lipline. she doesn't do sparkly gloss but highlights the center of her lip a little with a "highlight" gloss and tops with a shiny gloss (plain MAC gloss works wonders for plumping).

you have to be very careful with the top lip line to avoid creating a clownface, but it can be done nicely to the benefit of your friends features.

 

[Sojourner]

...

 

[MissPanther]

Mm, those are some good ideas I'll try it out and post a FOTD later! Thanks!