The "rule" is half plus seven. 47 / 2 + 7 = 31. She could date as young as 31 without it being weird or creepy. Congratulations, the age difference is officially* within acceptable boundaries!
* I'm no officiant, but this is what I've always heard, and it sounds good to me. I dated a 22 year-old at 19 and was told this.
Can confirm as creepiness limit