Needless to say, you were not negligent per se; you dutifully did your part until your daily routine veered off track. Since this can technically happen to any of us, there are steps we can take to keep from slipping up. Technological advances easily allow us to set an electronic prompt on our portable hand-held devices or desktops, while an unconventional bookmark manually inserted in our Sefer Tehillim can also serve as a reminder.
While prayers are unquestionably potent, none of us is immortal. Tefilla may sometimes postpone the inevitable, but everyone’s day must eventually dawn. Prayers on one’s behalf can also prolong the suffering of a terminally ill person in unbearable pain.
Another thought to reflect upon: Though we have freedom of choice, we oftentimes can clearly see or sense the Hand of Hashem guiding us – many times in ways we would never fathom or consciously choose for ourselves. You did not consciously choose to create the “void” in the group’s tefilla sequence; hence your doing so can be viewed as “meant to be” – for the woman’s time was up.
If you still find yourself dwelling excessively on this episode, light a candle for her neshama on the day of her yahrtzeit, or, if feasible, visit the cemetery and say some Tehillim at her gravesite. She will understand … and your burden will feel lighter.