Houllier said: "She took the right decisions. I was confident in her. She is good at what she is doing."
Massey was propelled into the media spotlight by off-air remarks made by presenter Keys and pundit Gray before the match between Wolves and Liverpool on 22 January.
Believing their microphones were switched off, they were recorded before the Molineux game suggesting that Massey and other female officials "did not know the offside rule".
Gray was sacked after further allegations of sexist behaviour came to light, while Keys resigned.
In the furore over their comments, Massey was removed from match duty because of the media attention on her.
She missed the League Two contest between Crewe and Bradford on 25 January as well as the Blue Square Bet North match between Corby Town and Eastwood four days later.
However, she did return to run the line in the 2-2 draw between Chesterfield and Aldershot last Saturday.
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