[Spoilers: Main] Was Rhaella in her 60s when she gave birth to Dany?

I’m just trying to get the timeline figured out between Aegon V’s era and Robert’s rebellion.

If Rhaegar was born at the fire of Summerhall and Daenerys was born 40 years later to the same mother that seems like a bit of stretch…even for the world of asoiaf. Am I missing an explanation here that was given in the books?