Basically I read the script and found it quite strange that there was such a huge age difference between the two. In the script it said that Jane Rizzoli was 30 while Maura Isles was in her late 30s [meaning somewhere near 36/37/38]

I don't think that Sasha looks so old though..

Wow, really? That's so shocking. I didn't think there would be an age difference like that, maybe two years or so? :)

They don't even look old at all. In reality, Angie and Sasha are a year apart, if I'm not mistaken..Angie's 38 and Sasha's 37. They don't even look like it though. :] So, I doubt Jane and Maura's characters are far apart.

In the script, they put it that way >_>

In the books Maura is older, in real- life Angie is a year older than Sasha, so for the series, I'm saying around the same age give or take a couple of years.

Well, on Maura's gravestone, it has her DOB as 1976, so she would have been 34 (cannon) in the first season.