Always look, before submitting credits, to see if there are similar/same names. You should, instead of typing in the name, use the unique ID number for her page, which should look like this form, nm9999999. It'll avoid the confusion.
Now you just need, though, to correct the credit. Go to the film/show page and click the yellow "edit page" button. Choose to correct one credit and click the continue button, then choose the name on the cast list that needs to be corrected and select it and continue. enter her number, or enter her name, then you get a list of similar names to choose her as her name is spelled in IMDb (if they are spelled the same, they are unique on IMDb because they have a roman numeral after their names). Check the box to explain and explain it's her first credit and was sent to the wrong page.