Who is the female Companion whose brothers were martyred alongside the Messenger of Allah, and who said, "Everything after the Messenger of Allah is bearable"?

Summary of the Answer:

It was reported by Al-Waqidi in Al-Maghazi that when the Companioness Al-Sumayra bint Qays suffered the loss of her two sons at Uhud, and she was asked about her condition, she said: "What has happened to the Messenger of Allah, peace and blessings be upon him?" When she was reassured about him and saw him, she said: "Every calamity after you, O Messenger of Allah, is trivial."