Okay, for starters.. thank you for a complete lack of visual aids. Ron Burgundy would approve of you keeping it classy.
ETA:This really is more of an Ask a Woman type question. But *teehee*since it involves women's sexual health I'll give a response ago. Just a heads up for future threads you might open.
The extra skin is probably a skin tag. Probably nothing to do with the size of her labia. Well, it absolutely has nothing to do with the size of her labia.
Like, why would the two be connected? Because "down there"
Labia skin and anal tissue totes different kinds of flesh.
Anyway, anal skin tags are caused by friction or irritation. They are easily removed with an office visit to a dermatologist. Some docs might send the tags to be biopsied, most won't without a family history of more serious conditions.