OP, over 500 replies and yet not once have you explained why you can't pump upstairs with a monitor
I explained upthread but will recap... being close to baby helps trigger my milk-letdown, also baby regulates breathing from mother's presence in room, and if he stirs or wakes I can attend to him before he cries (he usually sleeps through but sometimes wakes for feed, dummy or nappy-change). DH will not take out his earplugs as he has a long commute to work, needs to be up early. I'd rather he wasn't tired for work or driving. Also my pump is hands-free so I can comfort baby, retrieve dummy etc whilst expressing. If I was upstairs and baby started crying it would be full-blown screaming by the time I'd detached from pump and got downstairs (which would no doubt annoy neighbour more than pump). So it makes sense on many levels to pump in same room.
I feel I've taken reasonable steps to make pump almost silent for neighbour. Yes she can still hear it very faintly and if this very faint noise bothers her she needs to deal with her noise sensitivity (eg wear earplugs). You can't expect complete silence all night in a flat. What if the sound of me walking softly across floor at night bothered her, should I avoid getting out of bed in the night??
As for shift workers, I don't think you can expect them not to eat or move around a flat in the night! I once lived underneath lady who worked nights, she used to be nocturnal when off, I'd hear TV faintly, footsteps, cupboards opening, water running etc. That's part of living in a flat, you minimise noise but also learn to live alongside other people and their patterns.
at poster who thinks I should take my tiny baby out of flat for a few hours each eve. Can just see myself walking round the freezing park at 10pm with crying colicky baby in pram. No, he has every right to stay in his warm home and be comforted. Neighbour can always go for a walk/drive if she doesn't like the sound of him crying!