[S4M]

I never used Matlab, but I am very familiar with R which I think is quite similar. So I'd advise your girlfriend to just play with the Matlab repl (enter 1+1 and see that it returns 2, plot a function, assign a variable, etc.), and then write some function on a text editor and load them into Matlab.

You can also help her to load some data (from a text file, a csv file, or maybe a database connection, depending on what's used at her lab), and then do some basic operations on them (calculate some basic statistics and do some easy plots).

When she can do all of that (and I don't think it should take her much time to learn), she'll be able to work with Matlab autonomously.