Short answer: you can ask it to. Whether that helps depends on what you want the picture for.
ChatGPT and Gemini will both edit an uploaded selfie from a written prompt, lips included, and both have some free image access with limits. If you want to play with a general idea, or change hair and makeup at the same time, a general editor is the obvious place to start. It costs nothing extra if you already use one.
The trouble starts when you want to compare. Ask twice and you may get two different faces back. OpenAI itself notes that results can vary between generations, and edits can drift outside the area you selected. Typing "0.5 mL" into a prompt doesn't make the picture a 0.5 mL picture. It's a number in a sentence.
There's also no menu of named looks. You can type "Russian lips" or "Cupid's bow," and you'll get the model's guess at what those words mean, which may not match what your injector means.
A lip-only previewer like LookPrep is narrower on purpose. It has a fixed set of named looks, amounts you pick from a list, a separate lip flip option, and every option comes back on the same photo so two settings sit side by side. It does nothing else: no hair, no makeup, no full-face edits. The previews are still illustrations, not predictions, in both cases.
Either way, say the image is AI-generated when you show it, and let the provider tell you which parts they'd keep or change.
The full LookPrep vs ChatGPT and Gemini comparison goes row by row, including where the general editors win.
Sofia R., LookPrep