K-1 Visa and Marriage Changes
Marrying someone other than your K-1 sponsor on a K-1 visa is strongly discouraged. It can jeopardize your ability to stay in the U.S. legally.
K-1 visas are issued for the sole purpose of marrying your U.S. citizen fiancé(e) within 90 days. Marrying someone else goes against the visa's intended use.
This could be seen as misrepresentation and might lead to visa termination and deportation.
Marrying with the sole purpose of gaining immigration benefits is considered "marriage fraud" and is a serious offense. Penalties include deportation and potential criminal charges.
If your relationship changes, talk to an immigration attorney. They can advise you on alternative paths based on your situation and help you avoid legal complications.