Are you sure her mom sent that and not her on her mom's phone?
That's a possibility. It's also possible that her mother passed on the message and then told you her thoughts and her mother is sincere, but triangulating. It doesn't matter what her mother wants. My ex MIL told my ex not to leave me also. But it doesn't matter what mother wants, or even your ex (?). It matters what you want. It's this treating you like a friend?
You might be able to be friends later, but the hurt seems still too fresh on both sides.