Advice Needed: Should I Discuss a Past Mistake with a Marriage Prospect?

Assalamualaikum everyone. My father recently initiated a marriage proposal with a relative's daughter for me, and their family has agreed. The girl and I haven't spoken yet. Here's my concern: during college, I regrettably tried alcohol and weed, and it led to about a year and a half of use. I deeply repented, sought Allah's forgiveness, and stopped. I've been sober from alcohol for over three years and from weed for a year and a half. Alhamdulillah, even during that time, I remained committed to my faith. I believe in honesty and don't want to hide this from the potential, as it might cause issues later and doesn't feel right. However, since she's a relative, I'm worried that if this information gets out, it could damage my reputation-none of my family knows. If it's a deal-breaker for her, I understand and will step back respectfully. But if she tells her parents or other relatives, it might spread quickly, making it difficult to find another proposal later, as families often consult relatives for background checks. I could ask her to keep it private, but I'm unsure how to handle this situation wisely. Any thoughts?