Ranting and venting is fine 2fingers and healthy to a degree but it’s not always healthy to have an echo chamber either.
There are a variety of “shit cards” that life deals, infertility - while awful - doesn’t trump everyone else’s problems.
It’s very hard for the OP to have such trouble conceiving but that doesn’t mean her Mum doesn’t have a need to express how very hard her own pregnancy/birth experience was particularly when she’s emotional over her DD going through the same thing.
It’s very hard for the OP to have such trouble conceiving that that doesn’t mean that dealing with the physical aftermath of labour, emotional impact of post partum hormones and the mental impact of sleep deprivation isn’t very hard for her sister.
If her Mum is saying things like “hurry up” etc then she should honestly tell how those comments make her feel and ask her to stop.
But that’s quite different from expecting her family not to mention anything negative about pregnancy, childbirth and parenting because it upsets her.
Having children is indeed wonderful, so wonderful that it makes the hard parts worth it. But that doesn’t make the hard parts any less hard while you are experiencing them. Not even for people who have much longed for “miracle” babies.
Listening and providing support don’t always mean saying “there, there you poor thing, aren’t they awful”. Sometimes it’s about providing an alternative perspective or a kick up the arse.