My character needs to make a love choice but i don't know which character she should pick???
Question: Okay she is a mild-mannered surgeon and there are two choices of guys she could be with. There is Caleb the bad boy with a horrible rep. But she sees the good in him and will change him through the story. Then there is her good guy friend who falls for her, Ashton, and he is sweet and a really good guy. I think she should pick Caleb in the end but at first think she wants Ashton. What can Ashton do to conflict this feeling and make her choose Caleb???
Obviously, I don't know the details of your story, so I can't tell you for certain what the right answer is. However, you provide a big clue when you say that your main character provokes some kind of change in Caleb. That suggests that the real relationship story is between these two characters. In other words, the surgeon is the main character and Caleb is the impact character.
Every main character starts out with a particular way of handling problems and situations. In this case, I'm guessing that "who she is" at the beginning of the story is someone who might well choose Ashton, if Caleb didn't enter her life.
That being the case, Caleb will be someone who challenges her by presenting a different way of seeing things or doing things. In the course of their growing relationship, your surgeon must wrestle with whether Caleb
is right or wrong, whether she should start doing things his way or stick with her way. If Caleb changes after the climax, she will stay the same. If he stays the same, it will be because she adopted his approach. But along the way, either can "test-drive" the other's perspective, even if just temporarily before making the ultimate choice. (Of course, they can both change, but on different issues.)
The reason nice guys usually don't get the girl in romances is because nice guys don't challenge the girl. And yet, human beings need challenges to make life interesting.
So, it may not be that Ashton does anything different to make the surgeon reject him. He may just continue being himself. Rather, the surgeon starts to see Ashton differently because she starts to adopt Caleb's perspective, and that makes her see things about Ashton that she didn't before, or she finds herself bothered by things about Ashton that didn't bother her before.
Only you can decide what it is about Ashton that looks bad from Caleb's perspective.
Of course, if none of this feels right to you, keep playing with the story until it does. You could also make Ashton the one who challenges her and Caleb the kind of bad boy she is typically (and tragically) drawn to. The important thing is to give the real relationship a dramatic conflict - a battle of approaches - that must be resolved.