Initially the ending was balanced, but Black was too slow with her queenside counterplay and eventually mixed things up on the kingside.
38…Qh5. This is not a mistake yet, but the tendency is alarming.
39.Qe6 Rc6 40.Qe5 Qg4?! Repeating the moves to pass the time control looks like a good idea – 40...Rс8. 40...b5 is also playable.
41.h3 Qh5?! 41...Qg5 is mandatory, and after 42.Qxd5 Rc3 43.Qe5 Rd3 Black's drawing chances, despite the missing pawn, are higher than White's winning chances.
42.g4 Qh4 43.Qe8. Naturally, Tan does not fall for 43.Qxd5?? Rc3. Now Black's situation is alarming indeed, however, after 43...Qf6 44.h4 Rc7 she can probably defend successfully.