Your feelings are totally valid and it is difficult to receive this kind of message (nonsense) when you are grieving and to 'assume the best intentions' and to 'move on'.
Don't feel the need to respond right away. Allow your own emotions about your mother's death to settle a little. Death is a difficult process for those who are close to the ones that die, especially when the person who has died has human flaws. It is OK to reflect on her life as it was, in it's totality and to see the good, the bad and the ugly and to recognise your mother, as she was and as she was to you.
As you for your friend - when you are ready to examine that relationship, you may well be able to, in time, recognise that she too is a human with human flaws. You can choose to find a middle way between ignoring your differing views and carrying on, or distancing yourself.
I do find that in difficult times, our relationships with other people are less easy to navigate and the moments we need deep empathetic connection can reveal flaws in others, we find more difficult to gloss over. But take time, do not make any rash decisions.
Part of me would want to say - well if my mother is in hell, then for all her flaws, if there was a choice, I would rather be there with her, but as you know, I don't believe that there is a judgement process, because if there was, I think heaven would be a very empty place. But I would probably just keep that to myself and cry a little at the loss of something from that friendship.