While various mods for Stardew Valley allow you to marry non-vanilla characters, Jas Marriage Mod
If you choose to use the aged-up version, it includes several custom heart events to facilitate the romance:
[insert link to mod download site]
Do not demand a link. Experienced modders will often DM you a safe Google Drive or Dropbox link to a version they personally use. This is the safest method because the link has been vetted by a human.