Thanks for your query.
Unfortunately, ultrasonic fat cavitation is not advisable in pregnancy
It can harm a baby's developing immune system.
It can also damage the hearing of the unborn baby.
Apart from that, high frequency ultrasound
has various other side effects that are still under study.
These are all not 100 % likely to occur, but you cannot negate the facts that these side effects can and do occur.
As she is 43, she is already at high risk for abnormalities in the baby, which are maternal age dependent.
Ask her to contact a Genetic Counsellor to know the exact odds, and have a list of screening tests to undergo, following which she can decide what to do further.