I'm sorry for your loss. My mum died this year, and the grief has at times felt unbearable.
I think YABU for a few reasons. As well as losing my mum, I have also lost my dad and brother. I've never once visited anyone's grave, because, although I loved my family very much, it doesn't mean anything to me. I wouldn't take any comfort from it, nor do I understand why other people do it. My mum, dad and brother are not at their graves - they are gone. I don't need to set aside time to think about them either as I do it every day, a million times per day.
When my mum was buried, it was a bitter cold, windy, snowy, grey day, and at the end of the internment, the celebrant asked everyone to return to their cars so that extended family could have some time by the graveside and I remember think 'no way - it's freezing out here, and my mum would not want me to be cold'
On the other hand, perhaps a visit would have been too distressing for your daughter? Because for some people who are not cold hearted like me it can be overwhelming, and distressing emotions can resurface that are exhausting to deal with. Perhaps that is what your daughter can't be bothered with? Although not very elegantly put really, but I was not very thoughtful as a 19 year old either.
If you have explained to your children that you would like them to go with you to support you, then I can see why your daughter's response is a bit of a kick in the teeth, but other than that, grieving is personal and I wouldn't make her feel bad for not wanting to go.
(also - as my bereavement counsellor gently reminds me, your mum and the loss of your mum will never be fully understood by anyone other than you. Be grateful that your daughter doesn't understand the depths of your grief. She won't until it's your time to go and she has to grieve for you 
)