AITA for only getting a college graduation gift for my 28M son and not my DIL 28F?

So I’m a 55F and my son who I raised as a single mother recently graduated from grad school. His wife my DIL also graduated at the same time and I gave a special gift of a bit of cash just to my son because I’m proud of him as his mother and I feel a sense of pride since I raised him as a single mom. I figured my DIL had her own parents to gift to her. Well my DIL texted me saying she was very hurt that I only acknowledged my son (her husband’s grad) and not hers as she thought she was a part of the family as my DIL and they been together for a while. She said she didn’t expect the same amount of money of course but just a card or something. She said she felt like I overlooked all her hard work and only saw my son’s. However I don’t feel like I need to apologize or justify my choice in wanting to reward my son individually.

I could be the AH for overlooking my DIL’s accomplishment and only acknowledging my son’s.