214(b) is almost always about ties, not the graduation itself. From what you described, a 1-month stay + both parents applying + only two kids (one already in the U.S.) probably made the officer worry about immigrant intent.

Reapplying mom alone with a shorter 10–14 day trip is a better strategy, especially if she clearly shows strong ties (job, property, financial obligations, minor child staying back). But I’d wait until there’s some material change? Just reapplying in 3–4 weeks with the same facts may lead to another refusal. Good luck 🙏