I can't judge without knowing the diagnosis. I'd stay with the person more likely to die on me and the person less able to fend for him/herself and no other people to take care of him/her.
The fact that your mother came doesn't count because she had no one else in a life threatening condition to care for. If she'd had to chose between you and one of your siblings, both in serious condition, she would probably have gone to the one that best fit the criteria I outlined above.
Your wife may have thought that since your mother was there your critical needs were covered.
