An older parent

There seem to be quite a few moments recently where I'm finding that I'm struggling with my mother.

I am the sibling that lives the closest to her but also I've assumed, more or less, that I will take on the role of local carer.  I have a young child and I'm embarking on a new career, so I could never be the full time care for her, but I will certainly be the 'go to' person.

This is not happening yet or indeed in the foreseeable future, as my mother is very healthy and doing well.

But I am getting glimpses of something that I hadn't seen before.

She seems to be more vulnerable and also takes offense more quickly then in past years.

She assumes that when I'm upset about something and I'm showing it in my face, that it has something to do with her or she has done something or that I don't want her here with me.

And this is what she did tonight.

After a long story time, my daughter finally cleaned her teeth and climbed into bed.  Lots of kisses and hugs from me and her grandma, and her door was closed and I could finish off my chores.  I had a wash to get on, so I whizzed around picking up bits of dirty clothing and threw them in the machine.  Mum said something, and I simply replied that I needed to get the wash on before it got too late.

Next thing I know, mum is picking up her bag and leaving.  There is no kiss goodnight, just a good bye.

What do I do?  Should I just let it ride?  Was she offended?  Do I apologise?

This is really frustrating.  It's not easy being a single mum and I really do appreciate all the help she gives me, but I could do without these moody moments or is this simply a by-product of getting older?