Problem modding SHAR. Homer and Lisa silently stare at each other

Hi, I'm trying to mod the game, but I'm not very smart about this stuff, but still, I'm learning everyday something new. Many of you said that I should look at the game files to learn more, and it actually helped, now I thought that a good thing to do would be to modify a mission step by step, changing little details every time, so I'm trying.

But now I'm a little stuck because I tried to modify mission 2 (Pretty Theft Homer) and changed Ned into Lisa (I replaced avery single "ned" with "lisa" in my "m2i.mfk" and "m2sdi.mfk" files). Everything is fine at first. I talk to Marge, I go to the school and go in front of Lisa. But when I try to talk to her nothing happens. They don't say anything and if I press ENTER nothing happens, the mission just doesn't start (I can just press ESC). But the game doesn't crash or anything, they stare at each other silently XD, so I think that I should modify something else too and not just the files "m2i.mfk" and "m2sdi.mfk", but I don't know what... may you help me? :3 I don't think I have to do much more, just to modify another file or two.

Thank you in advance and sorry if I'm asking a foolish question ^^"