Individuals make their own decisions about whether they go to work or not. Some people are very stoic and work through pain and others whimper at the least little problem.

In terms of qualifying for Social Security Disability Insurance (SSDI), there is a 5 step sequential evaluation that is applied.
http://www.socialsecurity.gov/OP_Hom...6/416-0920.htm
Briefly:
Step 1 - Is the indivdual still working and performing substantial gainful activity? Determined by hours worked, help given to do the work and how much is paid for the work. If she files a claim before she stops working, she may be denied if she is still doing what she used to do for the same amount of money. If she is not, she will have to show a whole bunch of proof. If no, go to step 2.
Step 2 - Does the individual have a severe impairment that is documented by objective medical findings? What do the medical records show? If no, denied. If yes, go to step 3.
Step 3 - Does the diagnosed condition meet or equal a listing - a specific definition of symptoms required to be found disabled. Not just a named illness. In cases involving progressive illnesses, the day the individual stops working is often considered the date of onset of disability since that is the actual date that they stopped dragging themselves to work. If the symptoms meet or equal a listing (not just the name of an illness), a person is found disabled.
http://www.socialsecurity.gov/disabi...book/index.htm

If a person cannot be found disabled at Step 3, SSA goes to Step 4 - can the individual perform their recent relevant work? If yes, claim denied. If no, go to step 5.
Step 5 - can the individual, considering their age and vocational background and education as well as their medical condition, be expected to be physically and mentally capable of doing an easier type of work? If yes, not disabled. If no, disabled. There are people who want to do away with Step 5. If it was eliminated, there would be fewer, not more, people approved.

Since this is a legal definition of disability in the Social Security regulations, government employees decide if someone is disabled according to the regulations or not. There are some government employees with medical degrees, but most are trained to follow policies previously established.

There is an appeal process for people who are denied. The higher you get in the appeal process, the more legal issues are raised to determine if the medical evidence is evaluated correctly.

You will hear that everyone is denied SSDI the first time. Totally false. Urban myth. However, it is true that close to 2 out of 3 cases are denied on the initial level and the first appeal level. That means 1 out of 3 cases are approved.

There is a five month no-payment period after date of onset before benefits can be paid. There is a welfare disability program, Supplemental Security Income (SSI) that also exists, but the person has to be found not just disabled but also limited income and assets.

Read the stickies in this forum. Read everything you can at socialsecurity.gov. Do not assume that anyone's anecdotal story applies to your girlfriend. Do understand that the people who post to these forum are generally the 2/3 that are denied initially. Not everyone who files has a severe problem. Do not expect this to be a simple process. If approved, she will also probably be bringing in a lot less money than she did while working. Social Security Statements with benefit estimates are now available online at socialsecurity.gov. Do that before starting an online claim. And print it.