Is it known if the injury is from the attack or did he already have it?
Acid attacks require copious amounts of irrigation. Just continuous water poured for at least half an hour. If it gets in the eye, it needs to be forced opened and irrigated continuously with water running off the skin as quickly as possible. It continues to react and burn for a day or more even with treatment. If that's a fresh injury from splashback. He is going to need treatment and soon. A small bottle of water is not going to cut it.
I wonder if this was a revenge attack? As in, if that mark on his face is an older injury, perhaps this woman and her kids are connected/family to someone who attacked him in a similar manner.
Casting no blame on the victims here. I just think it would be a very strange coincidence for a man with significant burn injuries to his face to attempt to inflict acid-burn injuries to this woman's face.
Of course it could be the common reason this happens and she turned him down at some point in the past.