The pair bothers me. Julia is a full name, but Sylvie is mainly used as a diminutive. Why not Sylvia and Julia or Sylvie and Julie? I agree with the others, people might assume that Sylvie is just her nickname, or that Julia is actually a Julie. They might think that they misheard those names and autocorrect themselves.
Separately they are beautiful. I prefer -ia over -ie though.
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