I'm going to ask my friend if she was with her ex-boyfriend
Why are you going to ask her that?
Because I want to know if she is still seeing her ex-boyfriend.
Although you might be curious, you shouldn't pry into your friend's romantic affairs. You should respect her privacy.
I can't get my answers anywhere else, so I have to bother her with all this.
Your friend's relationship with her ex is her business and not yours. Getting in the middle of it is interference and should be avoided or else you risk creating a conflict between you and your friend.