Wow - all that information, and you still want more!
I'm sceptical about it being or having been a given name in statistically visible numbers. Tolkien used it as a Hobbit name; Hobbit women tend to have flower names, and the more weird or unlovable the character, the odder her name! Much like
Bertie Wooster's aunts, though I don't think Wodehouse uses Lobelia.
Dahlia, yes! My role model!
If I was considering Lobelia as a name, I think I'd be put off by the first syllable, which since it has the main stress would be the obvious one to use as a nn. And 'Lo' seems uninspiring ...