That's the thing, this doesn't seem like a heart to heart from the mother's perspective (from my perspective). The mother was just asking if the Kid wants to try acting, and suddenly she starts bawling and saying "I'm sorry" over and over again.
There's no reason for MC to deny wanting to try acting, unless I'm missing something?
You could say her failures in the last life made her want to not act, and that's the reason for the outburst - but from the mothers perspective this would still seem like an odd emotional outburst.
MC is a kid that acts far too mature for her age, always acting in front of everybody, closing her true self even to her mother, and the mother can recognize that all along. I mean, MC called her mother Akari in her mind, and the mother could have felt that. It's emotional because her daughter finally let loose her true self and stop acting. Those "I'm sorry" can be because of two things: because MC realized that her mother knew that she kept her distance and lied all this time, and because of all the inconveniences in the future caused by this selfish desire.
The mother knew that her daughter is extremely smart and mature. What would be the most likely reason as to why MC threw away her dream that the mother could think of? Money. Even thought MC actually just wanted to stay with the mother to repay her debt (she was not truly thinking of Akari as her mother and just acted like one).
Why would the mum need to earn extra money by selling herself? The daughter has already gotten a acting-manager's business card, that's already like the biggest hurdle over-come isn't it?
Or are we going to get some dumb acting classes arc where the mum desperately tries to send her to an expensive school?
Being scouted is actually the cheapest and easiest part (people got scouted on the street everyday in Japan).
Depending on their income, an actor can easily spend
thousands of dollars per year between classes, marketing materials, union fees and agent fees. Although it's possible to start acting for free, in order to get the best training, actors can easily spend thousands to train at a top drama school. Graduating from a drama school is similar to graduating from college; not absolutely necessary but it would
really help you get work.
You can read this 2019 article:
https://www.backstage.com/magazine/article/much-cost-raise-child-star-9990/
That's why the mother considered prostitution.