The warning about heavy lifting is sexist crap about how women should look.
We all need muscle, for health now and to help maintain independence in old age.
Build up your upper body muscles, with press-ups, pull-ups, bench press, tricep dips etc. so that it is in balance with a muscular lower half.
It's never to late to start: In studies, people in their 80s have improved health and musculature after starting lifting.
The only warning I would give is that women of 40+, especially those who have given birth, need to be cautious about pelvic floor / prolapses. Also be careful of your joints.
So, get a trainer to check your lifting form and build up the weights gradually and sensibly.
I'm 58 and I train intensively 5-6 x week at the gym: HIIT spin, heavy lifting, boxing, XFit (see my pix)
The others in my classes are very fit, but 20-37 years younger, men and women. I am still one of the fittest and strongest: Age is no barrier.
Yes, I have a lot of muscle - I'm proud to be a strong women
Go for it, OP !