is that 'lump' directly over her spinal area or somewhere else close too it? is she very active in like sports or doing anything overly strenuous that could have possibly caused some type of neck injury? just given the symptoms she is having, at the very least, i would try and get her into see your primary doc tomorrow if at all possible. having them do at least a basic x ray may show just what that lump actually consists of. it could be whats called a trigger point which is simply wadded up fascia/muscle from inflammation, or it could be having more to do with a particular disc issue, or something else entirely. that is why at least SOME level of look inside right now is simply needed. its that baseline that starts the process of real dx of any condition/problem we have.
is she having ANY other odd symptoms at all right now like a sensitivity to light or headache and anything at all that would be considered 'not normal' for her? she just does need this checked out. if all she had was that stiff neck from sleeping "wrong' that would be one thing. you could see if it just got better in a day or two, but with that lump being there over her spinal area, it just needs further evaluation by her doc, you know what i mean?
you could try some type of NSAID like aleeve(my personal favorite) which just lasts much longer than regular motrin or advil just to see if it has ANY affect on her ability to actually move her neck at all. if it does help,this is probably at least based upon some level of inflammation, which her doc also would need to know too. you just need to follow up on this with her doc to see what is the real underlying cause of this. hopefully it is just a temporary type of inflammation from something she did. please keep me posted on just what you find out. FB