I'm dealing with a similar load to you right now and it is nothing, absolutely nothing compared to having to deal with my eldest not sleeping. That made me physically and mentally ill and changed me as a person forever.
I like to think I would be sympathetic and supportive, having been there. Pre-children I'm sure I wouldn't have understood - I may have been sympathetic for a while but it would have worn off pretty quick. Now I know better and I'm just so grateful that I was in a position to not have to go back to full time work when it became clear that my child was (figuratively only, calm down) trying to destroy my sanity and kill me. I think a bigger issue is the fact that this is how so many women are forced to live now because we're not usually in a position to not work or to just hire a night nanny so someone else can deal with it. Of course it's not fair on colleagues to have to pick up the slack if someone really isn't handling their workload properly but the way we live today, mothers just giving up work isn't a solution either. Society needs to change but of course that's a different thread.
I want to comment on those pointing out that if she has another parent around this shouldn't all be on her because it isn't really that simple. I had/have a very supportive husband who would and did everything he could to help. Unfortunately I'm a light sleeper anyway, always have been - I can sleep upstairs and be woken just by the sound of a key being inserted into the front door downstairs. This meant that even sleeping apart so that my husband could deal with the nights I was woken by my child screaming so I still didn't get a decent night. Not just in the next room but on a different floor and the other side of the house, and even knowing he's dealing with it, it still isn't an easy thing to ignore and just go back to sleep. Sometimes she also didn't want him and could only be comforted by me. You also get into a bit of a vicious cycle or habit of not sleeping, so my child would go to my mother's for the night so we could both rest but then I'd automatically be woken several times during the night by my fucked up body clock and worried about my mother being able to comfort my baby and if they were OK. 50 hours without sleep? Yes, perfectly possible. My child did manage to get some sleep during that time due to sheer exhaustion but that doesn't mean I did because when I did manage to get her back to sleep, it would take me probably an hour to wind down and get back to sleep myself. Then within 30 minutes, maximum, she'd wake again. It was a similar cycle all day so there was no let up then even without having to go to work. I found I lost the ability to sleep properly at all after a while, as if my body had just forgotten how to do it even if I did have the opportunity.
I think those who aren't taking it seriously are those who haven't been there. I was terrified to have another child because of it.
On the plus side, @Bloopbloopbleep , having tried absolutely every trick you can imagine, I finally found a way to make my daughter sleep. She was three by then and I was just a shell of a person but I fixed it and I did learn to sleep and become a human being again. You'll get there too. Plus it doesn't really sound as if your colleagues have got anything to complain about. You're getting it done, you shouldn't have to feel you need to exceed normal standards.