Lately I've been noticing how Pyper is around other dogs. Around big dogs, she is great. I used to talk her with a roti/sheppard mix and they were amazing together(it was a female as well). But when she is around other small dogs, it seems to make her go crazy. I was walking her last night with my boyfriend and from across the street she seen a fairly small dog (bigger than her though) and started to bark uncontrollably. I just couldn't get her to stop. I was getting so upset/frustrated over this. She is normally a very good dog. But the second she started barking, she was all riled up and once the dog was out of site, she continued to bark. I made her stop, and sit and I tried to calm her down before continuing our walk. But it was of no help.
I really need some advice or suggestions on what i should do.
Is it that she is trying to be dominant against another small dog?
Is she not socialized enough?
Anything please

It is very heart breaking when she does this. It makes me feel like I am a bad owner.