Exercise for Pregnant Woman

My buddy’s wife is 6 months pregnant and would like to know of an exercise for the lower back that would be appropriate for her. She is experiencing pain that might be related to her extra weight and thinks that strengthening her back might help her out. A little background: she is athletic and has worked out in the past but has only been walking during her pregnancy.
My buddy says she has a big mouth but I don’t know what that has to do with this question.
Thanks!

I developed spine problems in highschool that made it nearly impossible to walk I was in such pain - and since I was a competitive runner I had a real rpoblem on my hands! this exercise was literally a ‘miracle cure’ Have her lay on her back on the floor, knees bent to 90 degrees with feet on the floor (as if she was going to situps) Feet should be at least shoulder width apart, and get further apart as she gets stronger. Now have her roll her hips up off of the floor hold a count and then put them down. 3-1-3 tempo. As she gets stronger she can spread her feet wider - this isolates the muscles and helps prevent using the hip flexors. She should notice a difference in just a few days. I started with 2 sets of 50, but she’ll have to guage what’s comfortable for her. When she’s ready for greater challenge, have her lift her hips off the floor, then rock her butt down to the floor and up to full ‘curl.’

Let me know if this helps!