It is Mothering Sunday on Sunday. This is the Uk's version of Mother's Day. The UK already had Mothering Sunday when Anna Jarvis began her campaign in the US. It was done in part to honour her dead mother (a renown peace activist) which is why in the US, the day happens around the 13th of May. In the UK, Mothering Sunday origins come from Lent and the tradition of returning to the Mother church on the 4th Sunday of Lent. As this meant often returning to where you came from, it also became about visiting your own mother.
When the International Mother's Day movement began, the UK simply co-opted the day rather than moving it to the 2nd Sunday in May. Some countries used the presentation of Jesus to the temple as a date ie Norway and Kosovo). Some use the vernal/Spring equinox (many of the Islamic counties such as Iraq, Saudi Arabia, Kuwait, Egypt, Syria etc)
It is a day to honour your mother -- whether or not she is alive or dead. Everyone has a mother. There was a colour code in the carnations (the first flower associated with Mother's Day -- white if your mother was dead, red if she was alive) It is about remembering how much your mother does for you and what she means to you. The day which Anna Jarvis worked so hard for was supposed to be about sentiment, not profit. Jarvis grew to hate the day because she loathed the commercialization.
It was supposed to be about telling your mother (or indeed the person who was your mother figure) about how much you appreciate her. Personal, not commercial.
Unfortunately the marketing focuses on living mothers, rather than on honouring all mothers. An idea to honour a departed mother would be to give a donation to her favourite charity. Or perhaps spending a little time looking through photos of her and remembering how special she was and the little things she did. (I do this on Father's Day as my father died over 25 years ago). A good mother never dies, she lives on in the things you do and the way you do things. And if you have children sometimes you do see your parents in them.
Mothers are important. I am very grateful for mine who remains very much alive. Although at her request, I honour her on the US Mother's Day, rather than on Mothering Sunday as she is American, not British as she has pointed out several times.