My girlfriend lies all the time!

I have a serious issue with my girlfriend because I think she lies to me whenever she can. It’s a compulsive habit she has had since she was a child, and I knew about it even before we began dating. She told me it was harmless because she didn’t lie about big things, but this is starting to become a problem because I have caught her out on multiple occasions, and she brushes it off as force of habit. I know she can’t help herself, but I am starting to doubt everything she tells me which puts a lot of pressure on our relationship. She doesn’t get it because she can trust me completely while I can’t say the same for her. I have begged her to try and be honest, but she thinks I am overreacting. I don’t think I am and I’m beginning to wonder if we have a future. Am I being realistic here?
If you can’t trust her, there is no future with her; it’s really that simple. If she doesn’t get it, chances are she won’t do anything to fix the problem because it seems as if she is refusing to acknowledge its seriousness. You may have to reconsider your relationship if things don’t improve, and maybe that kind of reality check is precisely what she needs to start recognising the damaging effects of her behaviour.

My boyfriend has friends who constantly belittle me. He never stands up for me and just laughs at them, asking me not to take anything they say at face value. If he lets them get away with this kind of disrespect, isn’t it a sign that he doesn’t respect me even if he says he does? 
Yes, not standing up for you condones their disrespect and they need to be called out for it. If he doesn’t take your feelings into account, he isn’t showing you what he means by respect. Tell him why this is a problem and confront his friends if he won’t do it.