No the offense does not become less serious, regardless of what their argument was, he lost his temper and kicked her. That is a crime. And no, she shouldn't be charged with attempted murder as she was only thinking of getting an abortion, she had not actually attempted to get an abortion yet. You can't punish someone for their thoughts.

Also, depending in which country this case occured, abortion might be legal, therefore he is still in the wrong and deserved his punishment.