[quote=@Danvers]
‘Her smile still playing mischievously at the edge of her lips.’

Playing would make it present.


Tbh it’s good feedback. Though may be getting flashbacks from my English lit A level 😂
[/quote]

Actually, it would be present if it was "Her smile still [i]plays[/i] mischievously at the edge of her lips." Which of course wouldn't be good for this type of writing cause we need past tense!

What you have there is a dependent clause, I think. So that sentence would be fine, PROVIDED THAT it's a dependent clause in some other past tense phrase and not just on its own. For example, "She walked alongside her friend, her smile still playing mischievously at the edge of her lips." That's perfectly fine and still past tense.  

But if the section was, "She walked alongside her friend. Her smile still playing mischievously at the edge of her lips." The second sentence, because of the "playing," is necessarily dependent and can't stand on its own, so this is wrong. 

You could also have it be correct put before the other part of the phrase. "Smile still playing mischievously at the edge of her lips, she walked alongside her friend." While technically correct, it reads a little awkwardly with such a short second half, so I would put the "playing" part second, though that's a style choice at that point, I think. 

Take for example this alternative as well:

"She walked alongside her friend. Her smile still played mischievously at the edge of her lips."

It's very clunky and while I don't think it's technically wrong, it would be better style to connect them somehow, either like the examples above or with some kind of conjunction: 

"As she walked alongside her friend, her smile still played mischievously at the edge of her lips." Or

"Her smile still played mischievously at the edge of her lips as she walked alongside her friend." I personally prefer the first example. 

Hope that helps! Do correct me if I got anything wrong. ^_^