very sad to hear about your friend's mothers death.
I think the best thing you can do right now is to just be there for your friend.
There aren't any great things you can say or do right now, because I guess your friend is just starting to grasp what horrible thing just happened, and maybe not ready to talk yet, so just be there and show that you care about her and are there when she needs you. - And then: be there when she needs you!
For the moment, I'd just show that I am are there. So call, even if you don't know what to say (and from experience, it's always better to say when you are lost for words than to use words that don't feel or sound right to yourself), just ask whether you can do anything. - Your friend might just want to get some disratction or just out of the house for a while, if lots of relatives are still over and things are still getting organised
Or why not go over to your friends place and just give her a hug, or if you can't go over there write her or her family a note and let her know you are thinking about her/them. Offer your ear and support and just be there and listen, even if your friend has nothing to say (yet). Just having someone there can often make things feel better.
Sending energy your way, so that you can support your friend through these rough times.
"Through repetition the magic will be forced to rise."