Answer

Thanks for the extra info!

If she is not eating much that can impact her ability to produce stool but if the fiber hasn't helped her pass anything then I'd be concerned there is another health issue giong on.
Drinking more and eating less can go along with liver disease, kidney problems, digestive tract blockage, a pancreas issue etc.

A spinal issue can cause inability to open the sphincter valve or move stool along the intestinal tract if the controling nerves are impacted.

Here is a quick overview of how I determine if a pet needs urgent care -

If your dog appears dehydrated (see if a pinch of skin over the shoulder blade stays stuck in a tent form or flows back down normally when released), is not eating or drinking, isn't urinating or passing stool, has a rectal temp over 103.5F (normal is 100.5-102.5 Fahrenheit or 38 - 39.2 Celsius ), has gums or tongue that look white, blue, gray or yellow tinted where they are normally pink, has a slow color refill if you press on a pink area of gum or tongue, is having difficulty breathing, or is becoming more lethargic and non responsive to you as time goes on then you may want to get the dog in to see a vet as soon as possible.

I'd suggest that an in person exam for your mom's dog is the best option.

Charitable giving is down but you may still be able to find some financial aid.

As cash flow is an issue, check with your local humane society to see if there is local low cost vet care, ask your vet if you can do time payments or here are some groups that might help you afford the vet bills:

American Animal Hospital Association
http://www.aahahelpingpets.org/
" Through the AAHA Helping Pets Fund, veterinary care is possible for sick or injured pets even if they have been abandoned or if their owner is experiencing financial hardship."

Angels 4 Animals
http://www.angels4animals.org/
"Our services range from financial aid to complete treatment
to those pets and pet owners in need."

Care Credit If you qualify this may work well for you.
http://www.carecredit.com/
A credit card company for health care, including veterinary care.
"With a comprehensive range of plan options, for
treatment or procedure fees from $1 to over $25,000, we offer a plan
and a low monthly payment to fit comfortably into almost every
budget." They have a zero interest program if you pay within a certain time frame and they list the vets who work with their product.


God's Creatures Ministry
http://www.all-creatures.org/gcm/help-cf.html
"This fund helps pay for veterinarian bills for those who need help."

Help-A-Pet
http://www.help-a-pet.org/home.html http://www.help-a-pet.org/
"Our efforts focus on serving the elderly, the disabled, and the
working poor."

IMOM
http://www.imom.org/
"We are dedicated to insure that no
companion animal has to be euthanized simply because their caretaker
is financially challenged."

The Pet Fund
http://thepetfund.com/
"The Pet Fund is a registered 501(c)3 nonprofit association that
provides financial assistance to owners of domestic animals who need
urgent veterinary care."

United Animal Nations
http://www.uan.org/lifeline/index.html
"The m ission of LifeLine is to help homeless or recently rescued
animals suffering from life-threatening conditions that require
specific and immediate emergency veterinary care. We strive to serve
Good Samaritans and rescue groups who take in sick or injured
animals. In certain cases, LifeLine can also assist senior citizens
and low-income families pay for immediate emergency veterinary care." They also keep a list of local and national help resources here
http://www.uan.org/index.cfm?navid=163

 

More groups here http://www.speakingforspot.com/helppayingforveterinarycare.html