Your daughter probably hears her father and grandparents refer to you by your first name during the day. Ask the adults who care for her during the day not to refer to you as Erica but as “your mother” or “your mommy” (or whatever you want to be called). You didn’t indicate whether she also calls her dad and her grandparents by their first names. If so, that may well be where she began the habit, and you will need to let them know that you don’t want her using that form of address with you. If not, point out to her that she doesn’t call them by their first names, and that you would prefer it if she called you mommy. If she calls you Erica, don’t respond; wait until she calls you mommy.
If I may editorialize a bit, I am sympathetic with your aversion to having young children call respected adults by their first names. However, the first-name pattern is widespread in our culture, not only with young children. Place an order over the phone and someone says, “This is Carol”; look at an item in a store and a clerk says, “My name is Todd, if you need help.” Some child-care teachers have the children call them by their first names (especially the younger workers). So you’re fighting a cultural pattern as well as expressing a personal preference. Good luck.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.