watercopter, what am I missing? It seems as though your ex's mother has already told you what she knows. If this is the case, why not let sleeping dogs lie?
Are "Emily" and "Chris" the same person?
In any event, an ex's mother would be the 10th from the 7th house, or radix 4th house, ruled by Jupiter. Mercury has passed its last aspect with Jupiter, an opposition, but it does apply to a trine with a 4th house Saturn. I suspect that the mother will not really want to talk to you but that you will be in communication.
The moon in your turned 12th house for your ex makes me think you already believe that deception occurred.