This is a difficult question to answer because I have minimal information but I will do my best. It seems as though you have two possible problems: one friend does not approve of your boyfriend and the other likes your boyfriend too much. Generally speaking, if there is a problem between you and your friends, it should be dealt with openly and honestly. Problems left unresolved could lead to degradation in the relationship. If you cherish their friendships, then this problem is better dealt with sooner rather than later.
You should not expect your friends to blindly support every decision you make simply because they are your friends. This would be an unreasonable expectation. True friends care about your wellbeing. When they disagree, it would be natural for them to discuss the matter. Dissenting opinions from individuals that you care about and respect should not be discouraged; they should be considered, analyzed and discussed. If your friend disagrees with your choice of a partner, then find out why. I’m not certain if you and she have had such a conversation but if not, you should.
It is not uncommon for adolescent and young adult females to have a very close circle of friends and when she meets a suitable partner, she disconnects from the group. If the relationship ends, in many cases the group will allow their friend to return to the circle. Sometimes, the friends are jealous or upset when a member leaves the group and it may cause a problem. It is nothing out of the ordinary and in the American culture seems to be the norm.
With regard to your friend who has feelings for your boyfriend, confrontation is not necessary. You want to be calm, yet assertive about your concerns. Keep in mind that you cannot alter your friend’s feelings that she may have about your boyfriend. Feelings happen naturally. They are not within our control. We cannot control who we are attracted to. While you cannot control your friend’s feelings, you can establish boundaries with her regarding how she behaves toward your boyfriend.
Finally, friends are an important part of our lives but so is the development of independent thinking. You have your own opinions and your own mind. You can elicit your friends’ opinions and take them into consideration but ultimately it is your decision.
I hope this helps to answer your question. If you would like to write back to provide additional details about your question, I may be able to give you a more specific answer. Please take care. I wish you well.