When Personal Milestones are impacting Professional Goals

I'm part of the founding team of a fintech startup. Our marketing manager heads a team of five. She's getting married next month and is super excited with the whole hoopla. Date outings, relatives, puja, invitations, festivals—it's just too much energy being redirected. We're happy for her, too. But now it's becoming a productivity issue at work. Things are delayed, nothing is on deadline, subpar work is getting published, and the numbers have dipped. She was hired because she's good at her work, but this is getting her distracted from what she's good at. And it probably won't stop after getting married. She'll be even more taken up with a new house and responsibilities. Ofcourse, I've spoken to her about this, and the response is the usual: "I'll do better, I'm trying, I'm aware of the delays." Look, as a female, I'm all for women's empowerment. But if you get sidelined in your efforts, someone else will get this job. She's good; I don't want to let her go. What do I do here? Please do not make crass comments on gender or call her names. This is a professional platform; let's maintain the sanity of the same.