I'm so sorry you're going through this DD3 has had bronch 9 times this past year (bloody awkward child!) so you have my every sympathy.
The major concerns with bfing (as far as the Drs are concerned) are that they can take a lot of milk on board which swells their stomach reducing room in their chest cavity for their lungs and making it difficult for the diaphragm to move freely.
Bfing can also use a lot of energy when they are struggling to breathe - DD3 used to hit high 80s/low 90s on O2 sats, the breath rate would go up to 60+ and reach 170+ on HR when bfing when she was really poorly.
She was syringe fed or NG tube fed when that was the case though the interesting thing was at ~3m/o she was 'restricted' to 23mls of milk an hour - the average milk intake for a 1m-6m old baby is 25oz a day (28mls in a oz) or 29mls an hour so I can only imagine they were basing their calcs on formula feeding charts (she was apparently on 1/3 rations).
She really wanted to be bf though she would suck her fingers in a bfing pattern whilst they syringed milk down her tube.
As a bit of comfort for you when she was on the mend and off the tubes her heart rate would drop down to healthy levels, her breath rate would come down and her O2 sats would shoot up whilst breastfeeding - she would gets melt into the feed.
Ask if they can do suctioning before she attempts to feed as she will be able to feed and breathe so much easier. If you can get this set up to happen before you think she might be hungry it would be best so she doesn't get too distressed i.e. probably about 30-45mins after last feed. They can use a fine gauge tube after a wide bore one if ness. to get the thick stuff and then the fine gauge to get the thin mucus and further down the nasal passages.
If you can keep expressing (do it in bed to get some rest) when you have the chance so you can get your supply up and running. Have the ward arranged for a hospital grade pump for you (if might need to be brought from Maternity)? It's also good to have a small supply in the ward fridge/freezer in case of baby needing a tube asap (I'm crap at expressing under pressure usually but did manage 200mls by hand in about 5 mins when DD3 needed to be syringe fed for the first time!).
Keep bfing if she's well enough and if she's not then letting her feed whilst syringing a little milk in to the corner of her mouth is ok too as an option before moving to the more heart lurking NG tubes.
All the best to your whole family and I hope your baby comes home soon. Many unMNetty (hugs).