I went through it in the mid 90's. Relatively young widow with 4 kids under the age of 12.
Not that we're allowed to sleuth the step-daughter
(or TS, really), but (total speculation as it pertains to her income) it's entirely possible TS is receiving a Social Security Survivor's benefit (payee) for her daughter, due to her daughter's deceased father.
Also, since there is only 1 benefit recipient at this point, assuming benefits are actually being paid, she is entitled to the maximum amount the SSA allots for families.
TS would have also received it until she married, but her marital status only affects her benefit, it does not affect the minor child.
https://www.ssa.gov/pubs/EN-05-10085.pdf
The SSA details are facts, the rest is entirely speculation.
No sleuthing was performed in this post.
Batteries not included.
Dry flat.
Do not feed after midnight, or get the creature wet, under any circumstances.
All other various disclaimers apply.