I'm so sorry for your loss @Pjrunner .
I can identify with some of the tricky feelings around being a single parent to an only child especially at certain times of year. I've been lucky that as my son got older the feelings eased and I'm now much more comfortable with it- I hope that happens for you too.
Putting pressure on yourself to provide a perfect Christmas is understandable because you want only good things for your daughter. But in my own experience this can cause overwhelming guilt and stress- often we are aiming at an unrealistic goal and setting ourselves up to fail.
Combine this with the understandable grief you're feeling and no wonder you're struggling.
Your DH is still so so young and believe it or not any memory of Christmas at her age will be non existent or hazy depending on who you talk to.
Please be kind to yourself. Maybe pick and choose a few things to do together which maybe you can do each year to begin to build your own traditions. It sounds like youve accepted that your mum is unable to step up in the way you'd like, which is a shame but you can't make her change.
My son is now 17. When we can we still go to a panto together, wander round the shops one afternoon buy a bath bomb and have a hot chocolate, decorate a gingerbread house (this has become more elaborate and ridiculous each year), watch A Christmas Carol. I felt similarly to you 15 years ago, but things can and will change.
We've weathered a fair bit together including my 10 year marriage to his step father failing this year. My ExH has a huge family and I initially thought the ensuing massive crazy family Christmases would be wonderful compared to what I offered as a single parent to one child.
They had good moments but they were also exhausting and louder than I am comfortable with. I often cooked for almost 20 and craved it all being over. His family have not contacted DS or I and I find myself surprised to be looking forwards to a cosy, gentle Christmas together. DS is a typical teen, I don't share my feelings with him. Yet despite him being an extrovert with a lot of friends he too has said this week that he's looking forward to Christmas day "just us".
You are enough for your daughter. You love her and you have it within you to provide exactly what she needs. Sending you a unmumsnetty hug.