David,
If you look at her death/burial record (one of the parish records) you will probably find a cause of death but medical knowledge was not that great back then, so it might not be the same cause of death a modern doctor would find. My brother is a medical doctor (pathologist) and every time I show him one of my finds for cause of death, he tells me: They didn't really know. A lot of people died from a feber (fever) which isn't very specific. I have had young ancestors die of things such as tuberculosis, but there are other causes of death which were common too.
Try the Genline site (if you are subscribed) or order this parish record from any Family History Center. This is an extraction of the full death record, so perhaps the cause of death won't be listed. You want the Döda records and also make sure you have the right parish. All the parishes in Kronoberg will be on this film.
Sweden, Kronoberg - Civil registration
Födda, Vigda, Döda 1872 - FHL INTL Film [197023 ]
This is the full birth/burial record for Långasjö parish. You should get a burial date (unlike on the above film) and perhaps a cause of death.
Sweden, Kronoberg, Långasjö - Church records
Döda 1861-1895 v. FI:2 (T05218) - FHL INTL Fiche [ 6111810 Fiches 1-3 ]
There is a medical glossary on the SweGGate site. Click on Dictionary on the home page and then look at the top of the page you reach and find the Medical link and click on that.
http://www.rootsweb.com/~swewgw/ If you find a cause of death, it will probably be listed there.
Judy