Not sure why you didn't check the links yourself before you responded to their email or before you removed the posts.
Because the member made a topic and said those were her recordings and wanted other's opinions. Anyway, it's still in the trash bin. I can recover it if needed.
Note that even if it was a recording the poster had made themselves, unless they also WROTE the song themselves it could still be a copyright violation.
So all those sites (many well known) that link to personal recordings on YouTube are violating google's terms. eeeeek! I can't imagine how many sites will be suspended if they decide to go down that route.
I would simply write back and make the best case you can, and forget about the idea that it's a "strike" against you. I'm not aware of any evidence that Google thinks in those terms.
I already emailed them before making this topic so maybe it's best if I wait for their reply before sending another email? Well, they did say that future violations may lead to a suspension, that's why I thought it may be another "strike" on my account.