The 45-year-old journalist, who rose to fame on The Big Breakfast, has been dating the Great British Bake Off star since they met at a Halloween party in 2014.
Speaking to lesbian and bisexual magazine, Diva, Anna said; 'That night was one of the most extraordinary, memorable evenings where literally the planets aligned. Something was in the air that night, and that was the night we got together.'
'There was an absolute understanding between us and we've been together ever since.'
Anna had recently split with her partner Charles Martin, who she was with for 18 years.
'The sexual adjustment is easy, the emotional adjustment is something else, as you know, a relationship with a woman is far more intense. This I have learnt. It's an emotional tsunami.'
The new couple kept their relationship secret for months until the gossip became too much and they confessed to friends and family.
'A couple of people called me saying - I've just heard this hilarious thing that you and Sue Perkins are together. I mean that's just absurd, it's ridiculous.
'I found that quite offensive and I put them pretty bloody straight - actually, it's not funny and it's true and you should know better - that was the only thing that threw me; all my friends and family were amazing.'
Sue Perkins with GBBO co-presenters
Speaking about her sex life with Sue, Anna admitted that she felt 'blessed' that the BBC Two star finds her attractive; 'We're just two middle-aged girls toshing about the flat.'
Her friends have all been supportive of her new relationship and even admitted they're all curious about a lesbian relationship; 'Every single female friend I've spoken to has said, "Ooh, I've always wondered what it would be like to go to bed with a woman", or they'll admit that that have but they just never talk about that.'
The biggest problem the pair have faced so far is Sue's fame and the attention it attracts in public, Anna admitted; 'People do the whole hysteria thing about Bake Off. That can be tricky.'