Other than petal shape it is very reminiscent of our native Stellaria holostea, so perhaps a member of the Caryophyllaceae?

I agree it looks like something in the pink family. It doesn't match any of our Stellarias or Silenes, so I don't know what to check next. Nothing is showing in my guides under Caryopherales. I've never seen this plant before. It could be rare.

Those leaves look familiar to me. Similar to Veronicastrum maybe?

Maybe, maybe not? I'm thinking it has to be in Caryophyllales, but what, I don't know? The leaves remind me of Silene, on a tiny scale.

That looks like it. Thank you! I've never heard of this genus before. It has to be M. lateriflora. It's the only species in my area.

https://www.illinoiswildflowers.info/woodland/plants/gr_sandwort.html