I can imagine why she feels stuck in the relationship.
They’ve been together for 8 years, and during that time Zoe has rid herself of every close friend she had that isn’t related to Alfie Deyes. She spends Easters, birthdays and Christmases with the Deyes’, Poppy’s the closest female friend she’s had in recent years, Holly, if I’m not mistaken, was Alfie’s friend/cousin first, Brighton is Alfie’s home town. Mark is the only friend *she* has left, but he was a fan of hers before anything else, and a sycophant even now (though I like him and do think he’d be supportive when they break up).
And I get it - she likes the way Alfie’s family operate, the way he’s been brought up, the way they’re still very close. They probably share values, politics, and life goals. Alfie, Poppy and Sean also have the same weird job she has. They understand each other’s work, and Brighton is the hot-spot for progressiveness and innovative careers in the first place. Alfie and Zoe even share offices there. It sounds like a match made in heaven - on paper.
I think, to her, her own family has become fragmented. They are no longer a whole. Her home is on the market (thanks to the user who posted about it being on rightmove - it’s lovely and Lacock is a truly idyllic place). Going to her parents probably doesn’t feel like going “home” anymore, but to some foreign, unknown place. I’m also pretty sure both her mum and dad have new partners and Christmases might be awkward and “unfestive” to her around them.
I can see how she might think of losing Alfie as losing family, friends, hometown AND Christmas all at once. That would be daunting to anyone. Zoe might not end up being the best wife or the best mother, and even if I haven’t been a fan of her business practices and ghostwritten lies in the past, I still believe family is more important to her than anything else. She lives on nostalgia, on simpler times when she watched Home Alone and her parents were together and Christmases were fun. She desperately wants family, and she desperately want to recreate her memories and regain that joy with her own little family. She likes rainy days because everyone’s home, having a hot meal and willing to indulge in her dreams of cosy togetherness. IMO she’s latched onto Alfie not because of some sort of extraordinary love, but because Alfie is the key to all the families she desires - his family and a new family.
Breaking up is hard, but it’s harder without your own support group. From what I remember, Zoe wasn’t all that supportive of Louise when she divorced Matt, and she barely acknowledged Pearl’s birth on social media. How karmic that she’s all alone now. I hope Mark and Joe will be there for her in the end. I can’t help but wish her the best.