@youngsally
I never had mood problems with Tamoxifen, or Aromasin--just physical ones. After three years on Tamoxifen, I did get a blood clot (known possible side effect) in my right calf and spent 8.5 days in the hospital and had to be on Warfarin for a year. While in the hospital that 8.5 days, they noticed I had anemia and I said not too surprising as my periods have gotten so heavy and hardly ever stop. Well, that led to a diagnosis of Tamoxifen-induced uterine cell changes (uterine cancer--another known possible side effect), so I had a hysterectomy. Then, I was on Aromasin for six plus years ('cause now menopausal for real) and from the very first pill, went "urp" all night long once I went to bed.

Here's a story of one woman's difficulty with aromatase inhibitors including mood swings, depression and joint pain; she weighed her cancer risks and the unpleasant side effects from the AIs she tried and quit it--https://www.curetoday.com/community/bonnie-annis/2017/08/the-choice-to-walk-away-from-aromatase-inhibitors.

Your friend's irritability and mood changes could be from menopause. My hot flashes were weird--I'd be so cold my teeth would chatter and the next minute, OMG, I'd be boiling; then, freezing; then, hot, etc. Continuing in that manner would have driven me crazy. I knew one woman whose hot flashes made her a prisoner in her own home--she never knew when one would hit and when it did, she would literally be soaking wet from the skin out (including her hair). Everyone is different--my mother had no problems; an 85-year-old friend said she never had any issues, but her mother, sister and a daughter did. If you have them, these menopausal effects are miserable and no, when you're standing there so soaking wet that you're making a puddle on the floor, it's not "all in your head." There are natural products and activities that she might benefit from as well as dietary changes that can help (eating some things and avoiding others)--https://draxe.com/5-natural-remedies-menopause-relief/, https://www.healthline.com/nutrition/11-natural-menopause-tips and https://www.healthline.com/health/menopause/alternative-treatment.

There's no reason for your friend to be uncomfortable (nor those around her), but she needs to accept she's having some problems and get some help. You don't need a drug, or treatment for every little thing, but ignoring some big issues is not helping her and those she interacts with.