On the one hand, you can understand Alex's wounded pride at having his girlfriend poison him because she didn't think he could win the duel. On the other hand, there's the knowledge that the Spirearch specifically ordered by Abigail and Grimm to prevent Alex from being killed, even to Grimm sacrificing his own life to protect Alex.
Sadly it seems out of character for Addison to tell Alex in the next book (to be finished in 2033) to get his head out of his fundament and marry the woman.