Mom in ICU after cardiac arrest, risk of removing ventilator?

My mom is 87 (F), just had her b-day on the 24th. 5"4, about 132 pounds, white. On Lasix and Synthroid. Has stage 4 cancer, breast cancer with mets to bones and lungs, but under control, no symptoms, tumor markers low. Has lived on her own, a month ago we moved her into assisted living where she has her own apartment and still does everything on her own, but no longer has to worry about cooking meals or remembering to take her pills.

On the 23rd, she had her chemo infusion (taxol), a bit later that day had horrible diarrhea. Gave her Immodium which seemed to help. Friday the 24th we went out for her b-day, she was fine. Saturday was fine. Sunday the 25th she was lethargic, and a bit more out of it than usual. Monday she was still out of it, and had a slight phlegmy cough - when I say "slight" i mean she coughed lightly maybe twice over 6 hours. I took her to the ER, they said her white blood count was low and indicated an infection, put her on antibiotics. Did a chest x-ray (or CT?) and said it looked clear. Later tests indicated pneumonia (which seems to be going around).

Tuesday evening she was fine, chatting, ate dinner, I left. Later at around 2AM the hospital calls and says she went into cardiac arrest; they brought her back and took her to ICU and intubated her. So she's now been in the ICU for 6 days, still intubated.

A few days ago, she was alert/aware, was answering questions by nodding or shaking her head, listening to commands like lifting her feet, etc. Now over the last two days she's confused, doesn't seem to recognize where she is, doesn't follow commands, just opens her eyes and moves her head around. We want to remove the breathing tube, but the doctors make it sound like aspiration is almost certain, which obviously we don't want to happen.

Her tests and scans actually show her to be pretty healthy! Heart is fine, EEG was fine, brain MRI didn't show sign of a stroke or anything. They drained some fluid from around her lungs and did a lumbar tap to check fluid for infection. I'm guessing that she has hospital-induced delirium, which isn't being helped by being on the ventilator. But they've said they generally remove the vent when the person is alert, responding to commands, etc. - I asked how that can happen if the patient has delirium and they didn't really have an answer.

I'm sorry this is so long! I guess I'd like to know what the biggest risks are of taking her off the ventilator in hopes of her improving cognitively i.e. of mitigating the delirium. Is there a way of lessening the chance of aspiration? We don't want to do a traech, as that seems too invasive.