JOEL - A living woman may only be sealed to one man. Since your friend was already sealed to her late husband she may not be sealed to another while she is alive. If your friend is getting married in the temple she is probably going there to be sealed "for time only" to her new husband. When she dies that sealing will no longer be in effect and she will still be eternally sealed to her first husband. While she is alive she could only be eternally sealed to the second husband if she had the sealing to her first husband canceled.