Linked In is designed as a networking tool for professionals. If these women work in the same field as you and may be useful in future job hunting, keep them. If they are random women added for no particular reason, delete them. If she objects to you keeping female contacts who have relevance to your profession, then wish her well with her single life.
That being said, why would your girlfriend refer to another woman as a bimbo? It's such a disrespectful term and frankly, it has no place in this day and age.
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.