She was able to change his diaper. But yeah, it would have made more sense to send Lara. In the pilot episode of Adventures of Superman Jor-El insisted Lara go with the baby but she refused and wanted to be with Jor-El.
I guess love for their children isn't very strong for Krptonians, Lara abandons Kal-El, Kal-El abandons Kara. At least Kal-El found a family for Kara. Lara had no idea what would happen to Kal-El. He just got lucky a kindly
couple found him.