It honestly sounds like you did everything right. I would’ve suggested everything you did. Credit freeze is #1, then passwords is #2. You did great.
As for your question, I’ve actually used several monitoring services and have had an overall positive experience but it’s definitely a mixed bag and YMMV. Some info I get is very specific and therefore helpful. Sometimes it’s extremely generic ie an alert that your primary email has been found on the dark web…. Ok, I would’ve gotten a similar repose with an “have I been pwned” search. I’ve been involved in like 15 days breaches, I fully expected that email to be found on the DW by now.
I also got these services all for free. One is permanent via my credit union which is great. I’ve gotten others as consolations from companies that have had breaches with my data.
I personally think it’s worth it to her even if she has to pay for a year or two and reevaluate from there, given her situation.