Wife's tolerance is crazy high for a newb.

So I was a casual smoker in college. But quit when I discovered pain meds which I was addicted to for 10 years. My wife, who has never once smoked weed, inquired about gummies to help with PMS symptoms, mainly insomnia. I bought some delta 9 gummies. 20mg's each. I decided to test it out and ate a whole one. About 90 mins later I was buzzed up like a mofo. Had the munchies and was a tad paranoid but not too bad. Definitely was high. My wife, who's typically a weakling with anything medicinal, can take a whole 20mg gummy and she never gets a buzz at all. She sleeps well on it. She takes one right before she lays down and within an hour shes out. But on the occasion that she does wake up in the middle of the night, she doesn't feel high at all. How can that be? She's developing a bit of tolerance for the 20's and is considering taking one and a half gummies now. I've just read too many horror stories about people taking gummies and going to the ER. But she's been taking 20mg's for about 3 months with no issues. Do you think she'll be ok upping the dose to 30mg? And how in the hell is she not getting a buzz?