Not necessarily. When someone says "I love you," it typically means they have strong feelings of love and affection for the person they're addressing. However, it doesn't automatically imply exclusivity or that they don't have love for anyone else.
Love is a complex emotion, and people can experience love for different individuals in various ways and degrees. Saying "I love you" to a partner doesn't mean they don't care for or love their friends, family, or other important people in their life. Love can be multifaceted and extend to various relationships.
If you're concerned about the exclusivity of your girlfriend's feelings, it's essential to have open and honest communication with her. Talk to her about your feelings, concerns, and expectations regarding your relationship. This way, you can both understand each other better and be on the same page regarding the nature of your relationship. Keep in mind that communication is key to a healthy and successful relationship.