How should I talk to my friend if she fancies my boyfriend?

Well you could show her the texts on his phone from her and that it is proof that she has been flirting, find ways of having proof like that or this may sound mean but invite her over with your boyfriend for a movie and then leave the room to make popcorn or to go do something and if she tries anything get your boyfriend to text you even a blank message to give you the signal she is starting to be more than friendly and then walk back in and catch her out, but it has to be done very slyly-if thats the right word. You can’t muck it up at all but its not the best thing to do. Um im sure there are plenty of ways in which you can do it. Maybe an easier way is to still have both around for a movie but get him to go out the room and try to talk to her. Tell her that if she has any feelings for him then you dont mind (even though you really do) but that you’d rather she’d just tell the truth because you want to be best friends but its hard if you dont trust each other. show her the texts on his phone and say you know he isn’t lying and that you would really appreciate it if she would just tell you what is going on. She might be jealous that you have a boyfriend or that he is spending time with you or more time with you than you are with her and ant to break you up to have you to herself, she might not even fancy him and think its the only way to break you two up. Saying he is lying and things like that if you understand where I am coming from. You really need a calm talk about it. Ask her if anything is bothering her and that you really love her as a best friend but you need to know what is going on. It will be hard to talk about it and you can’t expect her to just spill straight away but do it slowly and dont forget to remind her you care about her a lot more than she thinks and that she is still your best friend.

I hope I helped a bit. Sorry its long and sorry if its no use.