To me, as a Polish person, both these names without ł sound eastern or possibly Balkan, in which case and I can't really judge those.
Bogumił to me is an old man. A very old man. Or possibly an unhappy child.
Bogumiła is a teeny tiny bit more timeless. But I think it's mushy, I imagine her as lacking assertiveness. And I'm usually not proven wrong after actually meeting a
Bogumiła. It's kind of a nice sound but since she'll go by Bogusia anyway, I'd go for the slightly stronger
Bogusława.
https://www.behindthename.com/pnl/109883