Good work, Ellie! And kudos to the teacher for teaching and encouraging her student to create and compose!
There are many good things going on there ...
1. She (the student) is clearly working on the [a-b-a] form, certainly a good framework for new composers to be working in.
2. She seeks to create contrast between her "a" material and her "b" material, even to the point of pushing the "b" material into a different key (e.g., from major to minor) ... also good thing for new composers to do.
3. She is slowly expanding her harmonic vocabulary, from using only the I chord in her earliest compositions to also using the V (or V7) chord in her later compositions to also injecting the IV chord into her latest two compositions. Also, going from solid, whole-note chords to broken chords to Alberti-like figures in her latest compositions ... all are good progress to see in a young composer.
As far as constructive suggestions goes, there might be few things ripe for her to further explore ...
One is to merely inject tiny variations when repeating a previously-used material in a piece. When composing in the [a-b-a] form, she so far literally copies the first "a" section into the last "a" section. One thing to explore is to introduce one or two tiny variations when reusing old material. So the simple [a-b-a] form becomes more like [a-b-a'] where the a'-section is a slight variation of the a-section. These "tiny variations" need not be elaborate. They can be as simple as changing one or two notes, or changing a chord, or tweaking the rhythm a bit. (No need to do all of these, just one or two of these will do.)
Another is to attempt larger forms. She can, for example, group her first [a1-b1-(a1')] material into a larger section (let's call it the larger A-section), create another set of [a2-b2-(a2')] material (call it the larger B-section), then put together the whole piece using the [A-B-A'] form again. (The second A'-section being a slight variation of the first A-section.)
Third is to think about creating some sort of "bridge" or "transition" when going from section to section (e.g., create some sort of tension at the end of one section that resolves into the beginning of the next section), so the transition from one section to the next does not appear "sudden."
By way of example, I'll use her Haunted House (Book 2, Op. 5) piece to illustrate some of the things mentioned above. I quite like the Haunted House piece because I think the motif/base material has lots of potential and her original [a-b-a] construction in this piece flows rather nicely. She also hasn't get into the IV chord for this, so in essence holding the IV chord in reserve for "new material" that can be used to expand the work into a larger A-B-A' form. Please do not take the notes/chords written below literally (I did not even bother to copy her original accompaniment, just outlining the chords used) ... it is not my intention to write the music for the student, but rather just to illustrate some of the ideas mentioned above.
(If you want to print it out, download the PDF here: http://pianorecital.org/tmp/Ellie-Hounted-House-with-Ax-annotation.pdf
The B-section is "new" yet "not new" as it clearly borrows the rhythmic and melodic "shapes" of material from m.3 and m.5 ... but because the student has thus far held the IV chord in reserve, the introduction of the IV chord in m.9 makes it sound "new" to the listener.
If you want to further expand the piece, you can also imagine pushing m.8 into a V chord, then repeating the A-section with (a little variation) before going into the B-section, which would give you a nice [A-A'-B-A''] form. Of course, nothing says you cannot play the same trick on the B-section or the final A'-section to make this an even more elaborate piece ... just need to inject tiny variations here and there when you repeat old material to keep things from getting stale.
Hope this helps.