Alla sits next to 5 phonetic neighbors — Ella, Ala, and Alma are the closest matches by sound. Most share Alla's Russian-origin cluster, so the rhythm and vowel shape carry across the list.
You searched for names like
"all, everything, noble"
"shining, celestial light"
"lame, limping"
"free one, of the Franks"
"to soothe, to comfort"
"settlement of the Britons"
"prosperous friend"
"short form of Lavinia"
"from Clare, the bright place"
"from Leicester; possibly heavenly"
"washed, cleansed; or variant of Lavinia"
"bright, famous"
"of the Balbinus clan"
"from Lydia (ancient region of Asia Minor)"
"God will add, God increases"
Similar sound: These names share phonetic patterns with Alla — similar vowel sounds, consonant clusters, or rhythm.
Shared roots: Several names on this list have Germanic via Slavic origins, giving them the same cultural heritage as Alla.
Rhythm: Alla is a 2-syllable name. Names with the same syllable count tend to feel interchangeable when you're narrowing your list.