The article says the boy says they swam together but she never returned....not much other info to supply context and nuance. So details are missing but I do see the life preserver on the boy as a possible sign that the mom actually did love her son and wanted him to be safe. Unless the Holy Spirit reveals otherwise we have no other info as to what was going on.
Yes, it’s excellent that she didn’t throw him off the boat without a PFD, which she easily could have done.