Honestly, it's a great way to apply an isekai character (the isekai actually matters/means something and the plot is different because of it), and is quite refreshing and wholesome, with several tropes challenged during the plot.
And to add to oliv2079's defense: some kids with single parents feel like their parent won't be available as often if they get a new partner, and often act out as a result. So it's possible that Ariameru is intentionally saying vague things out of a desire to keep potential partners away, not from romantic interest. There could also be a lack of "ick" from her end due to already being 13 when she met the man who would adopt her.
Believe it or not, if the writing improves, we may see her—out of immature behavior—try to cozy up to the main character in a romantic way and end up going through some really painful and embarrassing experiences (to her) as a result of that. Teenagers are quite melodramatic, after all.
Not that I know for certain this won't become Usagi Drop; I couldn't really tell more than what the manga at chapter 15.1 is at. But, so far, nothing indicates that. Hopefully nothing comes of that other than my aforementioned future embarrassing memories of having acted out.
The story, so far, is worth checking out. I won't say the writing is amazing, but it doesn't suck, either. Especially on the attention to detail when it comes to caring for the little ones and how children that young need help with getting dressed and going potty in the middle of the night,
leading to one peeing his pants and that mess needing to be cleaned up (and the little guy needing some emotional ), etcetera.
The character designs are solid and the art is decent.