I am aware of Arlene but don't particularly like that name for my character, however, I am pretty sold on the name Arli. I think I would prefer a name that is quite different e.g. Alexander - Lex e.g. William - Bill e.g. Charles - Chuck I don't know why I am struggling so much
It doesn't have to be short for anything - may be her parents just picked it.....or maybe her name started with R and her little sister started calling her Rly and it stuck ( I know a guy who everyone calls Fuff due to it being his name as a baby)
Try this URL: https://www.babycenter.com/babyNamerSearch.htm?gender=FEMALE&includeExclude=ALL&includeLimit=100&excludeLimit=100&meaning=&origin=&theme=&startsWith=Arl&endsWith=&containing=&numberOfSyllables=&sort=
Names are hard if you actually come up with you own instead of using name generators. I particularly struggle with boy names. That being said, you should realize that the shortened form of some names go through some cultural touchups before they come out the way they do. Charles -> Chuck seems to have been spontaneous. Richard -> Dick seems to have been the result of some rhyming. William -> Same as above...kind of. So you are pretty much free to come up with anything on your own, even if it has seemingly no relation to the original name. Just chalk it up as culture strikes again.
A name doesn't necessarily have to mean anything. For example, when I'm coming up with names for my fantasy WIP, I just mash syllables together until I think the name sounds decent. (Galdin, Kaizo and Erysalia are just a few I came up with). Try and do the same with Arly? Arlyria? Arlyssa? Arlyssia? Arlynne? Or even just Arly? No shortenings. Why do you want this to be shorthand? Does it have to be? In the context of the story, does it fit her to want to shorten it or can it just be her name (like is she given a really fancy name and she wants to be seen as more casual)? Just some food for thought.
Thanks everyone - I've gone with Princess Aracyleasi who refers to herself by Arli for the sake of being less formal
Charlotte. It'd be a bit of a trip to get there but you could go Charlie and then shorten it to Arli.