I don't believe it's been established that she "obviously" was informed late.
FWIW I reviewed Memory Alpha (which granted is a wiki) and didn't see anything to suggest that Lien received late notice that she'd be leaving the show. Which doesn't rule it out, but I'd feel more inclined to believe the argument being made if it was mentioned there.
The only way she would have only found out that she was leaving the show when she got the script for The Gift (as Lynx alleges), would be if she paid absolutely no attention to the contracts her agent handed her to sign so that she would be paid for the 1st 2 episodes of the 4th season. She would have had to have been unaware that she hadn't signed a contract for the next three seasons.
I just don't think Jennifer is that stupid. She'd been in the business since she was a teen. She wasn't a naive kid who fell off a turnip truck.
She knew how the business worked.