from or since?

In this case I would use "from" because "a very early age" is kind of generalized or a bit vague. However, I would change it to "since" if it was referring to a more specific period of time or an event She's loved giraffes from an early age. She's loved giraffes since visiting the zoo for her fifth birthday.

I would go with "from". "Since" would be used if you were saying "since they were six years old".

From, I think, but they’re both probably ok.