I'd really appreciate some advice please as I am at a bit of a loss.
DSis is very independent and headstrong, always has been. She was a nightmare as a child and one of her worst traits was saying things without thinking about their consequences and then not really seeing a problem with 'telling the truth'. I love her dearly, we are very close and I let her faults wash over me in a way that I couldn't when we were growing up (much, I think, as she does with mine). She has, through dint of my DM's never-ending hard work, turned into a wonderful, loyal and great person to be with.
DM had a shit childhood with parents who hated each other and a mother who was emotional abusive. My DF is a wonderful man who came from a very loving and physically affectionate family - it's taken a long time but my DM is now very similar. It has taken a lot for her to become so emotionally open - even when I was little she saw some things as 'weaknesses' (or this was the impression I got anyway).
DM has had a rubbish year emotionally. She is stuck in a horrible job that (for various reasons I don't want to go into) she cannot leave. She doesn't have good self esteem and she had MH problems linked to this at the beginning of this year which resulted in her being signed off work. She also misses both of us dreadfully (I found out, from my Dad, that this contributed to her depression). We are both studying 300+ miles from home at opposite ends of the country and none of us can afford to visit outside Easter/Christmas etc.
I am very much a homebody - DP is the main reason I am here rather than living at home. I speak to both my parents every couple of days and my Mum sends me at least one text a day. DSis is much more independent and has a much harder time on her course than I do - her subject is more difficult and her university a better standard so she struggles to excel as she was used to at our bog-standard school. She also has a very active social life.
The problem is that she doesn't see the point in calling my parents more than once a fortnight. As we are very close at home, emotionally this is really hard for my parents, Mum especially. Dad is a bit more stoic and understands - I think Mum's issues get in the way: although she understands rationally, she has a hard time emotionally.
Unfortunately DSis told my Mum yesterday - after Mum asked outright - that she doesn't like Mum calling or texting every day or every other day (calling maybe one in three days, definitely one text a day - DM contacts her less than me because she knows DSis is a bit more independent). Mum is really, really hurt and DSis feels guilty for upsetting her but 'doesn't see the point in lying or taking it back - because that would be a lie'.
I don't know what to do. Mum has taken it as a rejection and I know, rationally, that she should step back but given her MH problems I don't think she actually can and I think telling her, however gently, to do so could really inflict emotional hurt on her. DSis acknowledges that it's a shit opinion to have that you want your parents to leave you alone - she's just said that if she had children in the future and they'd said that she would be devastated (this gave me the idea to ask on MN).
DSis wants my advice but, apart from suggesting she sends a card apologising for upsetting - but not for her opinion - I don't know what to advise. We have arranged that I will always text her instead of calling to make it easier on DSis (DSis will usually bluntly tell me to bog off if she's busy but I'm her big sister and I can take it - I know she doesn't mean anything by it). Don't know what to do about DM.
Does anyone have any advice please? I know this is long. It's all tangled up in my head and I don't know what to say to either of them - I don't want to tell DM that DSis didn't mean it because a) I know she did and she's been sounding off at me about it for ages and b) DSis will not take kindly, understandably, to me lying on her behalf.