If you want to refer to someone who is not a friend, here are some alternatives depending on your relationship or context:

• Acquaintance
• Colleague (if from work)
• Classmate (if from school)
• Neighbor
• Stranger (if you don't know her well)
• Peer
• Contact
• Associate

If you want a more neutral or formal term, you could just use her name or "Ms." plus last name. Let me know if you want a specific type of relationship or context!