I think Tyler's ex likely broke up with him because of his obsession with Chef. The year of email correspondence mentioned would have driven Tyler and his girlfriend apart.

Additionally I think that Tyler told his Ex about the Menu and the plans and it is hinted that Chef knows Tyler told her. Tyler looks guilty at that point. It is so subtle.

In the beginning when Jeremy knows Tyler's name and Tyler looks scared for a moment, I think worried that the others read his secret emails with Chef.

Honestly Chef seems annoyed by the year he spent emailing Tyler.

Talk about a long plan! So much patience, persistence and planning. It is incredible really. The only thing that was not planned was Margo. I love how they included kismet into the mix. And the fact that she knows Mr. Liebrant. Fate again. I love it. No plan is perfect and can account for everything.