Since she had a lump for a long time, implies to me a reaction.

Here is a site, which is very controversial but interesting:
http://www.whale.to/vaccine/point.html

Timing...
http://qjmed.oxfordjournals.org/cgi/.../full/96/8/611
I think people vary in the timing to reactions. To assume that they have to be immediate does not take into account that all people ARE different.

http://www.thenhf.com/vaccinations_25.htm

Adults get viruses in the ear fairly often. When vertigo cannot be identified, virus is often the suggested diagnosis.
These tend to resolve over time (can be months).

I hate to bring this subject up: huffing.
Kids that age will experiment with it secretly...since it is easy to get stuff to inhale.
A professional colleague of mine's daughter was doing this!
Freaked my friend out, majorly!
Good kids can get induced by peer pressure to "try" something.
So keep this in mind...and think about the kids she hangs with, etc.
http://www.usdoj.gov/ndic/pubs07/708/index.htm
And this is difficult for a parent and/or doctor to discover.

Also I'd investigate what is going on in Art Class or shop etc.
Solvents like xylol are used in silk screen printing and have neuro effects when used without a protective hood/exhaust system.

Also I'd look for heavy metals. Lead, mercury, cadmium, and arsenic may be found in
some paints/art supplies. Testing for these is fairly straightforward.

I'd also ask your daughter if there is anyone hostile to her, bullying her, competing with her?
Mean girls or boys can spike a water bottle with a drug, like LSD and cause terrible
reactions.
A gal at my old job who was order entry, had her water bottle spiked at work, and
she ended up in the hospital! A police investigation failed to find the person, and
the victim quit the job. Also a teacher in a school near us had his coffee drugged as a
prank/dare by a boy, and this teacher ended up in the psyche ward (reacting since he
was grieving his wife's recent sudden death). Mean things like this happen, and it
is not typically one's first thought.