Complex sentence: Jelena Gruba (fl.1391--died after 1399) was the Queen regnant of Bosnia from 1395 to 1398; the only female ruler in the history of Bosnia and Herzegovina.
Split into simpler sentences: Jelena Gruba (fl.1391--died after 1399) was the Queen regnant of Bosnia from 1395 to 1398. She was the only female ruler in the history of Bosnia and Herzegovina.