DA:O Changing companion race and head

You need to export gen00flleliana.utc
That will put it in "C:\Users\Username\Documents\BioWare\Dragon Age\modules\Single Player\override\toolsetexport\"
You can then move it to "C:\Users\Username\Documents\BioWare\Dragon Age\packages\core\override".

i.imgur.com/dFxD6ZN.jpg

You are trying to use an elf headmorph on a human character... and the postion of the headmorph (height-wise) is fixed... it doesn't change dynamically depending on the body it's attatched to. (That's one reason all same gender, same race characters in the game use the exact same body model).
And an NPC's race is one of the things that is set in the character's UTC file, and thus is 'baked into' the save file. It can't be changed on the fly (mid game) by altering the UTC, because the game doesn't reference that information after the first encounter with the NPC.

You MIGHT be able to edit a character's race by editing your save file, though. (Be aware that this is theoretical and entire untested!)

First remove your edited Leliana UTC file from override. Then try this:

1- Download and install pyGFF.
2- Make a hard save in a new slot, in case something goes wrong. (Call it something like 'racedit', so you'll know the correct save is being edited.) Close out the game completely.
3- Open the 'raceedit' save with pyGFF.
4- Expand the SAVEGAME_PARTYLIST node.
5- Expand the SAVEGAME_PARTYPOOLMEMBERS node.
6- Expand the gen00fl_leliana node.
7- Expand the SAVEGAME_APPEARANCE node.
8- Select SAVEGAME_CREATURE_RACE. That value determines a creature's race.
The available values (not all of which are playable races) are:

1 Dwarf
2 Elf
3 Human
4 Qunari
5 Animal
6 Beast
7 Darkspawn
8 Dragon
9 Golem
11 Demons

So you want to change the value in that field from 3 (the current value), to 2 (the desired value). Make your edit in the 'Edit' box, in the lower left hand corner of the editor. Save the edit by hitting the 'Save' button just below, and then finalize the edit by saving the edited file (File>SaveAs). Close pyGFF.

Sorry the save edit didn't work... it was, as I mentioned, a theoretical solution.

I don't understand what you mean by 'change the headmorph with the GFF editor'... in your screencap, the morph you want is appearing, but you don't have the correct body model to attach it to...

There's no way to change the morph from one that is assigned to the female elf race/gender combo, and make it a human female morph, if that is what you are asking, or to alter the locational parameters ('height') for a morph (and all of the associated 3d models, like hair and eyes) so it can be used by a different race.

A while back I had Merrill as a warden and made Mhairi and Sigrun Dalish elves.
Mhairi on the right Sigrun on the left.
i.imgur.com/ZxOSnCD.jpg
But I changed the utc's before starting the game.
What I suggest is you start a new game, then bring up the console and type runscript selectparty
And see if she looks right in a new game.
If so, save the game. (Don't use this save to play the game)
i.imgur.com/JpmKf8Q.jpg
She looks a bit different here, because I have a Iona head morph in my override.
You wouldn't need that if you want the default Iona.
Then you may be able to copy Leliana appearance from that save to your old save.
I've never tried this, but it might be possible.

EDIT: I just tried it and it worked.
With the Elven utc in my override, my current save Leliana was borked like yours is, so I just copy and pasted this one line from the new test save to my current playthough save.
i.imgur.com/V7QiLzh.jpg
And there she is, Elven Leliana in the deep roads.
i.imgur.com/jAW82fA.jpg
Her portrait picture might be a bit off center, here she is set up to my regular Leliana morph.
You can adjust that in your portraits.gda

Her armor/clothes is from Kirkwall Exports www.nexusmods.com/dragonage/mods/3098
The tattoo I got from DAII Merrill for Origins www.nexusmods.com/dragonage/mods/4568 But I made it a bit smaller to fit the face better.
The head morph I did myself, but you will need a few mods to make it the same.
Dracomies textures from Dragonage Redesigned www.nexusmods.com/dragonage/mods/686 (You can install just the textures without the rest of the mod)
Eyebrow Presets www.nexusmods.com/dragonage/mods/1321?tab=files
Better Makeup www.nexusmods.com/dragonage/mods/4473
Pineappletree s Vibrant Colors www.nexusmods.com/dragonage/mods/153?tab=files (Just the skin colours, you don't need the eyes)

If you want my head morph, utc file and the modified tattoo, let me know and I'll put a link to dropbox with them in.

Here she is going through the joining.
i.imgur.com/TAkfIAQ.jpg

www.dropbox.com/s/yq2x7fohvuyf966/Merrill.zip?dl=0

There you go.
You should be able to just extract the merrill folder to your C:\Users\Username\Documents\BioWare\Dragon Age\packages\core\override folder and provided you have the texture mods listed above, it should be good to go.
I included the ef_bed200_merrill.mrh and a jpg of how she looks in the toolset.
Open that in the toolset and see if she looks the same.
If not, we'll have to look into what files are missing.

I also included the files for her armor, as I had edited the colour of her skin to make her arms a little less stark white.
I'll call that a fix or improved feature and it will fall into the modification permission.
If you already have Kirkwall Exports installed, I suspect the erf files will take precedence over these loose files and you won't see the changes, but I'm not sure, I only ever installed these files without the mod.
If you choose not to install the full mod, you should at least download and endorse it.

And here's my head morph and utc to make the keeper look a little more like her DA2 self.
www.dropbox.com/s/c7n6tw4yq0at6vg/Keeper.zip?dl=0