Among the artifacts in the Hidden History of the Kovno Ghetto is a photograph of Shulamit Rabinovitch's June 1944 letter to her sons in Palestine. The photo is credited to Shmuel Elhanan. It is interesting that the date is given here as June 27, not June 6 as in the Ethical Wills book.
The caption includes this information: "Shulamit Rabinowitz was deported with her husband and child. They survived camps in Germany and eventually were reunited with their family in Israel."
With the new date information and the timeline, we can now place the letter as having been written 12 days before the start of the week-long liquidation of the ghetto, when the remaining population was rounded up for deportation to Stutthof and Dachau concentration camps.