It’s much easier to be a gentile than a Jew, so there are old traditions to turn away prospective converts a few times. If she was turned away altogether it’s because they didn’t think she was serious about it, and that’s for her benefit. It would be actively harmful (spiritually speaking, but there are plenny temporal difficulties as well) to allow the conversion of somebody who didn’t intend to follow all the additional rules.
But the “Noachide” thing is still really weird, even for a Reform temple. Maybe she was so wishy-washy that the rabbi couldn’t bring themselves to actually convert her and just kind of made something up allow her to participate in the Jewish community without actually converting. Or maybe there are synagogues out there who do this to boost their numbers and establish ties in the wider community. I’ve just never heard of anything like it.
Yep, and this concept has ruffled a lot of feathers here and elsewhere. “You can’t tell somebody they’re not allowed to leave a religion!” It’s another spot where it’s easier to think of Judaism as a tribe. You can leave your ancestral lands, cast away your cultural trappings, reject those traditions… but the tribe is still there and you’re still a part of it even if it’s no longer a part of you.
Plus, the rest of the world has spent a few thousand years beating it into the Jewish psyche that ‘but I converted!’ doesn’t cut it when they come for you and your family.