My condolences on losing your sibling. Wonderful of you to take her in.

What’s the source of the regret? I just turned 30, and am still undecided.

Huh, I kinda feel the opposite. You need (or at least SHOULD) be very attentive to a pup. Dogs, in general, tend to crave/require more attention. Cats are more hands-off, so they often attract the kinda people who want a pet for the sake of having a pet - which tend to be narcissistic types.*

*not true of all cat people