I live overseas but her memory/mind seems to be deteriorating.
We FaceTime and speak on the phone a lot; i speak to her more than most people do and I know she's a bit lonely.
I'm worried about her because of the way she talks sometimes,
For example she'll spot I have a new curtain in the background and say oh they're nice where did you get them, and we'll have a chat about it. But then the next day or a couple days later when we're talking again she'll do the same. Sometimes for up to two weeks.
If I mention something Like oh the washing machines broken, have had to order a new one. A week/few days later she'll ask me if I've got it, I'll say yeah I love it works great. Cue another 2 weeks or so of her asking me if Its arrived yet! 
She also seems to make stuff up in her head,
I had a bit of bother with the last place I rented from. They accused me of damaging the floors (I didn't and in the end they conceded and retracted the bill and accusation that I'd damaged them - because they weren't even damaged.)
On a seperate occasion a friend came over and one of her dc spilled water on the floor and I slipped and hurt my foot a bit. My mum knows both things (the latter mentioned in passing).
However my mum now has it in her head that my friend damage the floors. I've said countless times that there was no damage from this and it was a completely different room that the Agents accused me of damaging (they accused me of damaging the dining room and bathroom floors, the spilled water incident happened in the kitchen.) so everytime I mention the friend my mum will say "oh god I wouldn't be speaking to her after the damage she did!" Or she'll randomly say something like "do you still speak to x? Did she reimburse you for the damage to your flooring?" I don't think my mum is being like this on purpose I just think she might be getting her wires crossed/confused to a worrying level.
She's always been a bit forgetful but this is a whole new level. To the point where I do get very frustrated when I speak to her and our phone calls are becoming less frequent.
I've considered dementia but I'm not sure that's likely as she's only 49.
Aibu to be worried and can I do anything? She's in the UK but I'm not. There aren't really many people I could talk to about it either - her and my sister aren't speaking as my sister owes her a lot of money (in the region of £10,000.) my nan has severe dementia and doesn't have much time left and I don't really have anyone else I could discuss it with for different reasons, so with that in mind if I'm not being U what can I do?
I've tried to address it directly with my mum but she swears she's fine...