Laura, what at first seems coincidental turns out to have meticulously planned by Theresa. She invited Isabel to NYC - and her alone - knowing that Isabel is Grace's birth mother. The visit to coincide with Grace's wedding, so she could bring Isabel together with her birth daughter. The wedding also meant Oscar would be there and that is also part of Theresa's plan: to reconnect the two former lovers. All of this, plus shutting down her business, is tied to her terminal cancer. All the twists and turns of the plot are about Theresa attempting to orchestrate a 'new' family once she is gone with Isabel playing the role of mother - to Grace and the twins - and perhaps even lover (with Oscar).

A coincidence is only a coincidence if there is no human causality behind it. We may experience those events as coincidence, but once the human intention is revealed, we see come to see them as part of a plan.

The tricky thing is not to lose the audience: "Come on. That's *too* many coincidences." So how and when you reveal the causality is key or else the script reader may check out.