Helllo RememberToPlaywiththeKid. So sorry your mum's having such a horrible time. Cakes is right, as her BC Nurse should be a good advocate. Meantime, am not sure if I can help, but I had 3 x Taxotere as part of my chemo and have just finished (hooray!).
Taxol and Taxotere are v.closely related, so I'd guess that's why they moved her from one to the other. Taxol is given weekly, Taxotere every three weeks. Just so you can compare, I found the first 10 days of each 3 week cycle on Taxotere tough, then felt progressively better until the next round. I'm guessing your mother fainting after 3 days is about when the steroids leave her body. They won't give you the drug unless you take the steroids as they counter an allergic reaction. Trouble is that the steroids have a profound effect, which might explain why she suddenly collapses. I just felt extremely tired at that point, but surely the Oncologists can find a way of helping her so she doesn't collapse?! I know some women taper off their steroids rather than bluntly stopping, so possibly something like that could help her.
From a distance, I'd guess her/ your best option is to try and nail her Oncology team - could you go to an appointment with her - or maybe you already do that? I'm not sure where she is, but my team would always see me if I called and needed a chat, so could you set that up asap?
On a positive note, her body reacting so strongly might well mean it's blitzing the cancer, so maybe suggesting that to her might cheer her up. I know my Oncologist cheered me when I was on my knees, by saying that.
One last thought, but a fair few women have their doses of the drugs decreased. My Onc told me that if I kept on taking the drugs at the strength they'd initially prescribed, I'd be seriously ill as it was obvious they were giving me what in effect was an overdose. To be fair to them, all they can do is guess how much to give each person based on an individual's weight and height. They can't tell until you've taken it how much the drug will hit you. My dose was decreased by 20% and after that, though I still had strong side effects they didn't hospitalise me, so they might decide to do that for your mother.
Really hope she gets some help soon. She's been horribly unlucky to have such a grim start to it all. Wish her my best, and feel free to ask any questions you want to. I'm sure we'll all try and help if we can.