While you may mean well and are excited to help a fellow Lolita along down the path to Frilly Rufflebutt-dom, you must first make sure that they will be able to accept constructive criticism or suggestions without getting offended. If they don't have a vested interest in Lolita fashion and only dabble in it for fun, it is probably best to let them do what they want and only give them critique/advice if they actually ask for it to avoid coming off as a Lolitist (Lolita elitist).
So if you are sure your friend really wants to become the best lolita she can be, how can you help to steer her in the right direction without making it into a bootcamp?
Share
Browse your favorite Brand websites together for inspiration and just to window-shop!
Go shopping for Lolita-friendly basics together at your local mall.
Do some simple crafts together! Check out my Sparkle Stitches tab for some tutorials that may be helpful :)
Exchange clothing if you are a similar size to try on new styles
Exchange accessories if you are not a similar size - it is still fun!
Practice altering store-bought clothing together.
Discuss
It's fun to have somebody to share with!
Talk about your dream dresses, favorite styles, what works for you, etc.
Offer each other concrit. If you give your friend the chance to correct you, she will be more willing to let you correct her!
Find coordinates or your Lolita idols online to compare and take inspiration from.
Gently point out any ita faux pas from online pictures that your friend may be committing. It is more gentle than directly saying she is doing something wrong.
Be careful of your wording if you friend asks for concrit. Say, "I think this looks better than that" rather than "This looks bad." Or criticize the clothes rather than the person, e.g., "The skirt would probably look better if it were pulled up to your natural waist," or "The proportions of the outfit look more balanced with a belt to cinch in the waist," rather than "Your legs look short and stubby and you have a muffin top when you wear your skirt too low."Record
Take photos of your outfits so you can both keep track of your progress. It's more fun when you have somebody to do it with!
Post online. You can obscure your faces if you like. It is less scary to post pictures together if you are nervous!
Make timelines together to see your changes.
Create a collaborative scrapbook.
Research
Go through helpful resources together. You can both learn from them! It also feels more like a shared experience than a lecture :)
How to avoid being ita by F Yeah Lolita
How to create an awesome coordinate by Ramble Rori
Lolita Tips on tumblr
Tips for plus size Lolitas by Part Time Lolita
Even though livejournal is a very old system, I really do think it's a great resource and you don't have to update your journal with your personal life if you want to (or you can and just filter the posts!)
*You can follow Brand blog RSS feeds
*You can join communities for your favorite brands
*Daily_Lolita is a great place for inspiration from real people
*EGL is chock full of information and tutorials! Use the search function or check the memories!
Facebook now has many Lolita communities. You can find a community for your local Lolitas. It's easier to go to a meetup for the first time if you have somebody you already know there with you!
You can also friend other Lolitas that you meet online if you wish, but be careful of how much you share! I generally only add Lolitas I have known online for quite some time because facebook makes it difficult to filter what is shared. Livejournal is an easier medium to use for online Lolita friendships, in my opinion!
Google+ is also gaining popularity and it's easier to control what is shared with whom.Polyvore is a great site to make sample coords and check out coordinate ideas from others! (add me if you join! I love to see others' ideas!)
I hope these tips are helpful! I'd love to hear any suggestions that you have to share or perhaps your own personal experiences.
Good luck, have fun, and don't be afraid to experiment! Fashion is fun, and nobody is perfect all the time~