Berahino was reportedly hit by team-mate James Morrison when he apparently refused to apologise for a mistake that led to Cardiff's late equaliser at The Hawthorns.
The club have sought to play down the incident, saying it was a minor scuffle that was over in an instant and that it shows how much the players care.
And Mel insists he will be happy to select striker Berahino, 20, for the final seven games of the season - starting with Saturday's crucial trip to Norwich - as the Baggies battle to avoid relegation from the Premier League.
"I've been impressed with Saido, he's worked very well this week," said Mel.
"In addition to being an excellent player, he is also intelligent. He has shown this in training. And I'm sure he will continue to show this.
"They solved the situation between themselves in a perfectly natural manner almost as if they were two brothers from the same family.
"Saido seems to be more responsible than other people of his age and I told him that I trust him and trust that he will continue to work well.
"I've spoken to him throughout the week. He is very positive. He will be important to us in the final seven games."
Mel did not want to elaborate on what happened in the dressing room last Saturday, saying only: "Eighteen young sports players have come in disappointed.
"It's normal they would argue among themselves. After that it's normal to have a beer and forget about it. The players were disappointed they hadn't won the game for the supporters."
One thing Mel was disappointed about was that the incident had found its way into the press.
He said: "The dressing room is the home environment. If any news gets out, that is bad news for us. What happens in the dressing room, should stay in the dressing room. I hope we have a positive reaction from this at Norwich."
Although West Brom have been keen to stress the incident is in the past, they were forced to issue a statement on Wednesday night with quotes from Berahino denying he was considering legal action against Morrison.
Berahino posted a cryptic tweet on Thursday with a quote from the Bible, saying: "A patient man has great understanding, but a quick-tempered man displays folly."
The tweet was subsequently deleted.