Apparently May Hariri has trouble breathing normally through her nose. After a failed rhinoplasty, she ended up with a pinched nose tip.
This limits the air passage just above her nostrils, making it difficult for her to inhale enough air!
You can notice this in some of her close up photos, especially those in which she is taken from the side.
This is also why sometimes her voice sounds nasal, and that can’t be very flattering for a singer.