To be concerned about sister?

[Spename84]

My sister about the past few months has started to cancel plans a lot more and is constantly saying she’s too exhausted to go out and at least once a week tells me she’s getting another cold and feels ill yet when I see her the next day she doesn’t have a cold. I don’t think she’s lying about it I think she does feel unwell but I think it’s through mental health thats making her feel bad not a permanent cold which she says it is. I calmly suggested this to her just saying it maybe could be a little bit mental health. That’s literally all I said and she went crazy saying that I’ve been talking about her behind her back and that she never cancels any plans etc except one time (it was the 4th time since the start of january) what got me though was straight away she said that I’d been talking about her. I don’t mind if she wants to cancel. I would never force anyone to do something they don’t want to but I am concerned about her because it has been slowly happening for a while now and I don’t get why she would think I was talking about her to others just by saying that. Was I being a horrible person by suggesting it could be more to it that just getting colds all the time? It was only a 2 minute conversation before she hung up on me.

What's your relationship usually like? Do you see each other alot? It could be mental health, stress etc, but she could also just be after a bit of alone time. People go through phases. I know i do with my family.

We are really close and we see each other a lot. If one of us doesn’t feel like doing something we’ve always just told each we can’t be bothered. I don’t mind if she doesn’t want to go but usually it’s days where something isn’t properly arranged where we’ll go for coffee or something but she has started doing it for planned things. Like yesterday it was my daughters dance show. They do one once every 2 years and it was their last one. It’s ok she didn’t go but it’s just more she’s starting to cancel things like that now. I had bought a ticket for her and we had all the arrangements sorted then on the day she cancelled. I’m just worried about her as it’s not like her cancel things like that and she always says it because she has a headache or her body is aching and she will sit under her duvet all day. It’s turning into several days a month like that now. Last week she phoned in sick to work and did the same just for one day then was ok. I feel like it is more of a mental health thing than her actually having a cold/illness.