To be clear, I don't have a problem with writing a longer description of something usual as long as that description illuminates something. The corners of her mouth tugged upward into a smile is just a long winded cliche for she smiled. It adds nothing. If the reaction "he smiled" or "she smiled" is turning up so often that the reader is getting bored with it or feeling empty, throwing in lips tugging this way and that is not going to fix the problem or fulfill the reader.
The real problem is (as I stated upthread) the misbegotten notion that every line of dialogue or bit of action requires a character to react by making a face. There are roughly a billion things you could do in a story other than have characters make faces at each other. Yes, you need to show their reactions but those reactions do not need to be limited to smiles, frowns, blushing, and eyebrow quirks or wordier variations of the same.
Years ago, I beta read a novel that had a ton of great things going for it except that the characters constantly made faces at each other. In every scene someone would smile, someone would smirk, someone would blush, someone would scowl, someone would quirk an eyebrow, someone would roll their eyes and someone would frown. To make a point that the writer wasn't getting, I copied a scene and replaced every instance with MADE A FACE. It helped the writer see the problem. I highly suggest this exercise to anyone so tired of writing "smile" over and over that they're tempted to blather on about tugging lips.
Seriously.