I can't find a source for ちゅうら.
Without an explanation, it isn't clear what relevance 清ら has to the entry. I don't think the x-ref is needed.
美ら and 美しい aren't etymologically related. I don't see a need for the 美しい x-ref.

@@ -10,3 +9,0 @@
-<r_ele>
-<reb>ちゅうら</reb>
-</r_ele>
@@ -15,2 +11,0 @@
-<xref type="see" seq="1486360">美しい</xref>
-<xref type="see" seq="2220810">清ら</xref>
@@ -18,0 +14 @@
+<gloss>pretty</gloss>

Interesting.

Official usage of 美ら:
http://oki-churaumi.jp/
Contemporary manifestations of 清ら:
http://www.churashima.net/churabito/index.html 美ら島物語｜美ら島・清ら人
http://www.okitour.net/Column/sightseeing/kannkousisetu/00213/
http://i-uchina.com/emotional/post881/

Added a second xref.
Reason: Although 美ら is widely (and, as the first one of the cited websites shows, quite officially) used in Okinawa, i just heard from someone that etymologically the expression ちゅら (ちゅうら) derives from the same root as the old (obsolete?) Japanese 清ら 【きよら; けうら】, so i looked 清ら up on the web, and, yes, it is alive in Okinawa (the last cited reference gives a more detailed explanation)

@@ -15,0 +16 @@
+<xref type="see" seq="2220810">清ら</xref>

Well, you probably know the old line that a language is a dialect with an army.
It's convenient to put 琉球語 and アイヌ語 in that category here.