Is it permissible to pray Maghrib at home during Ramadan in order to accompany one's mother at Iftar?

There is no blame upon you for missing prayer in the mosque to feed your mother, who is unable to feed herself, due to what the jurists have stipulated: that fearing for a close relative and tending to their needs is among the excuses that permit absence. However, if she is able and there is no fear for her, then you should not miss the congregational prayer at the mosque. And if you do miss it, then pray in congregation with your household members.