Trying to remember a book I read in the 90s

[CanIhavedessertfirst]

It was a YA thriller where a teenage girl finds her mum's old diaries and comes to the conclusion her mum was involved in someone's death. I remember, at the end, she meets her mum from the airport.

OP now it's the holidays there are more posters around, so maybe someone will have heard of this, so bumping for you.