Firefly is not very good at adding an exact text to an image (as is the case with other AI image generators). Occasionally it gets it perfect, and it is better than it was originally, but it still frequently does not get it exact and misspells a lot of words. I recommend that you not rely on Firefly for that and take a firefly image into Adobe Express and use Express to add the text. You have a lot more control over the font, size, etc in Express. Depending on what you are creating, you can add the speech bubble in Express as well. I do this all the time when creating Memes. 😁
You can take an image into Express by clicking the "more options" icon and select "Edit in Adobe Express".