The pop singer's appointment divided Strictly fans - with many feeling Alesha was too inexperienced, and others angry Arlene Phillips had been ousted.
But Tess told a British newspaper: "I genuinely think Alesha will make a great judge because she's got an opinion and isn't afraid of expressing it.
"As well as being gorgeous, she's got a big personality… she'll be exciting to watch."
She added: "I don't want to sound disloyal to Arlene by saying that – I'm hugely fond of her…I'm really going to miss her."
She'll be juggling presenting the series with caring for the new baby and her four-year-old sister Phoebe.
Luckily husband Venon kaye – a TV presenter and Radio One DJ – is a hands on dad. "It's not easy going back to work when you have a new baby, but Vernon is doing his share and that means a lot," she tells the Daily Mirror.
"We don't have a nanny so we manage the child care between us."
Stars doing battle in this year's Strictly include former EastEnders Natalie Cassidy and Ricky Groves, Ronnie Wood's ex-wife Jo and boxer Joe Calzaghe.