@Moonbeam: Margaret isn't sure what the situation is, she's just going on hunches and educated guesswork. Her initial correspondence would just be a simple offer of help, along these lines:
Dear Miss Quayle,
I read of the recent events at Master Leonin's workshop. It is my suspicion that the causes of this incident involved energies that are difficult for your former Master to comprehend, and that you are being unfairly blamed for its outcome.
I imagine that you are feeling confused and angry about this sudden turn in your fortunes. I believe that I may be able to offer some unique insight into the phenomena you have experienced, or at least to hear your side of the story with a willing ear and an open mind.
Yours,
Margaret Ashdown
(contact details also provided)