You did not indicate if your mother was still at home or in another facility. There may be services available through a nursing care or even assisted living facility which require travel when living at home.
The end stages of Parkinson's disease are neither pretty nor dignified. But there are some therapies you can do obtain for her to help ease your mother's pain/discomfort and possibly bring some symptomatic relief...(Symptomatic relief sometimes means less medication)
About the end stages themselves, you can read about through the various rating scales. As has been mentioned, patients manifest different symptoms and different rates of progression; however, there are some commonalities.
In the article below, you will find the 2 most common rating scales and links to the UPDRS and the revised version.
Has your mother gone to or been seen by a speech therapist who specializes in PD and/or stroke? It is still possible that there would be benefit her for her speaking, swallowing and breathing. Her neurologist should make a referral to a specialist. If that is not possible, please see the link below to an article about vocal exercises which can be done at home. There are a few articles at the site about breathing exercises and also voice exercises:
I would also suggest that for an improvement in quality of life - for feeling better, you inquire after medical massage. Because different states have different qualification for either licensing (as is done in my home state of Ohio) or certification, please distinguish between medical massage and spa massage. They are not the same and if not done by a professional can even be harmful to your mother. A medical massage therapist will work with your mom's doctor if requested. Don't forget there is a decided endorphin benefit from regular massage.
Take a close look at your mother's entire treatment and therapy regimen. Review it with her doctors. Since she has a feeding tube, I assume that she is on IVs, patches, possibly liquid forms but I could be wrong. Look at what kinds of exercise she can do now? What are her other options. Push to think outside the box.
Without taking a bite out of her rapid progression, it may continue at this rate.
If you are her caregiver, please get back up. Sometimes it is easier for someone else to have insight into what will help even if it is just brushing her hair or doing her nails.
One afterthought. Make sure that she can breathe easily through her nose. Sometimes there are sinus issues which can also impede swallowing and cause choking.