Daughter's Fibromyalgia / ME condition

My daughter recently moved back home after a failed relationship.  She has for many years suffered with chronic pain.  Since she moved back home I have seen how bad this is.  She lost her Job when her relationship broke up and she had to move away from where she lived to be back with me so she never claimed benefit given she lost her Job via those circumstances (is that right or wrong?) .  She has only just managed to get a job, though this is part time, part time as in short contract, it will only last the Spring / Summer season working in agricultural nursery.  No sooner did she start work thann pain and fatigue kicked in severely . . She looks so ill.. she is exhausted. Luckily her work is literally next door to our home so not far to walk.  Her skin is covered in small yellow bruises , (on her face and area's that are not possible to knock). This comes and goes but again doctors don't give reason, she photographs them as by the time a Doctors appt is available they have faded..  When she gets home from work, she showers then she falls into bed 7pm.  She is on anti-depressants but she now is  continuously  crying from the pain, the painkillers subscribed do no work.  She is now saying she is doomed,, she says she can't work because it exhausts her and causes so much pain.  She is only 20 and her symptoms first appeared around 5 years ago but were intermittent , now they seem constant .. but doctors simply issue anti-depressants.  She has had blood tests... scans / ultrasounds .. some will say Fibromyalgia , some say ME but none offer a way forward.  Her knee is giving way when she walks .. she doesn't sleep and when she does she has vivid nightmares.. She says she think she may have to quit this job as she is letting them down  and is constantly stopping to rest but she desperately wants money for simple things in life.. We are no high earners and budget ourselves but I have had to pay her prescriptions,  feed and do the best I can for her as if she were still a young girl again  ....  I see many mention claiming DLA or PIP.. I have no idea what the difference is?  is there something she can turn to as an income ? if she makes it to the end of summer in this job, should she try for DLA .. or job seekers?.. though I simply don't see how she would travel to any job when she can barely walk .. we are stumbling in the dark and have no idea what to do .. she needs hope.. I worry for her state of mind.. she has self harmed in the past too..  ;(