Wow, Lily and I have way to much in common, this is what I looked like in high school on my last day as a senior. They were giving away free books in the library, and i could be seen bipping along, with an armload of 20 or so books... Sadly no lovely gentleman was kind enough to give me some help. Love this though, you've really captured the book obsessed good girl that is Lily Evans.
The conversation sounds fine. Just, normally, instead of 'someone's' 'your' would be said when talking directly to someone like that. So it's "Do I look like I need your help?". But, both how you have it and like that work perfectly. James' question is a tad awkward to me, but it communicates, which is all that matters, really. I'm just used to hearing "Perhaps you need some help?" rather than "Maybe you need some help?". Perhaps and maybe are pretty similar when used like tha - so, it doesn't really matter. But, really, your English is just fine. Much better than my French. XD
Aw, they are so cute! If you wanted to make James' dialog sound more natural, you could change 'probably' to 'maybe', or take 'probably' out all together. But it is still very good! Lily's hair looks so pretty, and I love how James is wearing his uniform (again)
Hm... well 'maybe' means there's a possibility, and 'probably' means there's a very good chance. And I know you must be thinking, well, they would both make sense here, but a native English speaker wouldn't use 'probably' here. It's not a big deal, and only something you could know by being around English-speaking people all the time