When Are Characters’ Names Too Similar?

One of my beta readers for Death Out of Time thinks the names of two characters are too close. I don’t think I agree. But I’d like to get some input from readers and fellow writers. The reader in question doesn’t normally read science fiction. And that’s what this book is.

The two characters are both women who have small roles in this book. They’re humans from further up in time than my main characters. In their culture, women’s names are all 3 syllables in length and end in “a.”

So I have Udana and Edura for their names. Do you think these are too close or not? I haven’t set up polls for this blog, so if you’d like to respond, please leave a comment. Thanks in advance for your help!