Complex sentence: Gabriella was her father's only legitimate child for two minutes before the birth of her twin brother Jacques and was the first in line to the throne and Hereditary Princess of Monaco (as heir presumptive).
Split into simpler sentences: Gabriella was her father's only legitimate child for two minutes before the birth of her twin brother Jacques. As such, she was the first in line to the throne and Hereditary Princess of Monaco (as heir presumptive).