artists_beware | Problem with an Art Trade

Hello, I this is my first post here, and it's not a beware... it's more for advice. I hope the situation does not escalate to anything bad, but I recently completed an art trade with someone last night. There is a vast time difference, so I found she commented on it in the afternoon. The person really liked the piece, replying with:

Arrh! she is so cute! Thank u so much! and i looove the pose! <33 But she is a little fat? x.x it dosen't matter she is F*cking cute! <3 Thank u so much!

I replied with: I'm glad you like her!

I wondered that as well, but normal wolves are around that build

http://www.jon-atkinson.com/Large%20Images/La_Grey_Wolf2.jpg

I'll still fix the picture for you if you wish c:

Now I don't mind crit on my work, I actually encourage it, but it's the last comment that concerned me. The other artist replied to my comment with:

Yeah they are so cute xD
But no I'll do it myself but if u want 2 then your welcome! it's only the back

What concerns me is someone going back and editing a picture I drew. I know she has the right to go an mess around with the picture after I gave it to her, but I would like advice on telling her that I preferred if she doesn't edit the picture with out sounding rude.

EDIT: After a short conversation with them, I realized that I got the build of their character wrong. She wanted an anorexic-style wolf, and because I thought all her art was stylized I drew a wolf with a normal build (all her art has the character drawn really skinny). I'm now very weary of doing trades with this person, because I asked them to change something on her half as well (she spelled the character's name wrong). I asked her a day ago, and after asking her again today, she told me she JUST deleted the piece. I find this very suspicious, and a sign she just didn't want to do something so simple ( I have no idea how to feel about this). This situation is making me weary of doing any more art trades, but I'm sure this will happen every once in a while. I figure I'm worrying over nothing. The deleting piece thing was just a miscommunication. In the end, I'm just going to edit the piece, and then close art trades for awhile and work on personal art for awhile.