Hawk Girl and Vandal Savage sorta have this already. Except one is a superhero and one is a supervillain.
Hawk Girls dies and is reborn as the same person with all her memories from her past lives. Memories and powers tend to come flooding back in high-school, she does something heroic that makes the papers, and Vandal Savage starts tracking her down again.
Vandal Savage occasionally complains that his wives and children die and he doesn't, but he's an uber-rich super-villain. The few times he's monologued about it made the character even less likable.
Hawk Girl complains much more often about unfair it is that she is hunted by an uber-rich super-villain. Even she seems to think living forever with her past memories would be nice if she could just take a reincarnation off sometimes.
Immortality is usually seen as a blessing, not a curse
There are cautionary tales, such as Tuck Everlasting, but immortality is generally greatly desired and quested after. Mythology like the Fountain of Youth is built on everyone's desire to live forever.
The mom lives forever straight up. All she has to do is pop out a baby every 75 years. This seems like a small price to pay.
She knows her kid will get all her memories back soon, let's say around age 10. Mom knows she just puts up with a crying, snotty kid for 10 years and she'll get an adult trapped in a child's body.
Armed with the experiences of an adult, teenage years would be far less traumatic. Kid will have already acquired the soft-skills you need in a past life. Since mom knows your basically an adult, she probably won't be too strict with bedtime or discipline.
Passing on wealth would be simple too. One of you genuinely gets reborn. Mom pops out the kid. Mom raises the kid and puts her in charge of the family business. Mom goes off to have fun and leaves the kid to run things for 20 years.
Kid makes new best friend Mom! I mean Lisa. Lisa inherits the business in kid's will. Pops out the kid again. Repeat!
Psychologically, the worst part would likely be children + grandchildren not being in the (rebirth) loop. Sadly, many families lose young children. Mom and Kid would at least get to see their children live long full lives, and be there for great-great-grandchildren.
I think you'll have to add something like Hawk Girl/Vandal Savage to make it a punishment. As it stands now people will be lining up outside the witch's door!