Cheng Meng Festival

My mum passed on 6 months ago and we performed rituals at her resting place last month to celebrate her first birthday after her death. Is it Ok to visit her resting place again so soon after our last vist to perform cheng meng?? Is it OK to perform cheng meng on the actual date for fresh soul or do we observe the 3 days before or 3 days after the actual date
Thank you,