Izula 2 is a nice light choice, decent for neck carry, belt or pocket. ESEE-4 is getting a bit big for pocket...
Here's my thought, let her handle the 4, see if thats a good size, or if you need to go smaller, and then roll the 4 along on the trades and see what comes of it. Depending on what she wants, the 4 might be great, for example my wife's camp knife is a fixed griptillian, not a small knife by a lot of standards, but it makes her more comfortable in dingo country.
I love my ESEE-3, but I have tiny lady-like hands, so it works well for me. from memory, the 3 has a similar length, but narrower handle, so that might be a consideration the the 4 is just too big. (I might be wrong on that though)