Without question, weight training has been the best outlet from my professional + social life. for decompressing and preserving my body's well-being, specifically with regards to posture and mental focus over 8+ hour workdays.
Many conservative training cycles later and I'm squatting/deadlifting over 200kg.
Like you, the only sad part about it is how hard it can be to persuade some men and women to take part in the sport. Some people have major hangups about their body image, injuries and discipline.
I don't know if I'd recommend a personal trainer for anyone seriously considering it, trainers aren't cheap and most people aren't likely to stick with weight training. If we're talking weightlifting as a sport, yes you should definitely be working with experts whether trainers or fellow weightlifters.
I'd recommend anyone new to study up on form when you start working out, and maybe ask a trainer at the gym you go to to give you a quick form check.
Please don't be rude in comments here.
The big thing for me was not having off-limits foods. If I want pizza, I'll have pizza, but I log it and adjust my intake for the rest of the day to get those macros balanced. This kills the "I want it because I can't have it" temptations and has the effect of pushing me towards more naturally-healthy foods, because I can have 2 gigantic chicken breast instead of a piece of pizza, and I know which one is going to satisfy me more.
Also doesn't help that Healthcare in US is so ridiculously expensive that a single mistake will cost you months of salary.
I recently went to extremely low reps with the heaviest weight I can lift. My strength is now increasing rapidly, and it's far easier/shorter than slogging along with 3-4 sets of 8-10 reps each. Only downside: I need more rest. I _never_ hold my breath and go to great lengths to ensure my breathing is steady as I do every lift.
Before I tried this I did the best I could to ensure there were no tendon weaknesses and that my joints were in good condition.
Have her try to stick with exercises that are more upright ab exercises. Roman chair is a better choice than sit-ups.
Also, gluteal exercises that don't put too much weight on the back help as well such as leg extensions pushing back with that foot strap on your foot work well.
Anything is better than situps, since situps don't actually work the abs and are murder on the back.
Weight training is great, in moderation, like anything else.
You can train both and improve in both to a non-trivial level.
Strong people can get in shape, though. Take a look at crossfit athletes.