Hi Hannah,
One of my favourite iPhone apps is Hipstamatic. Nowadays it has become my preferred camera whenever I go to make a picture with my phone. Why I think Hipstamatic and other similar programs are so popular is that they force upon us different way of seeing the world. Rather than the perfect, colour accurate images that we tend to get out of most digital cameras now, we are instead given an alternate view of the world, something that most of the time we would be too scared to dial-up or invent for ourselves.
Now, as much as I love these apps and tricky programs, I also think that we need to take control of them from time to time.
A classic example is this “Holga” like image of yours. I think this is a great portrait your friend; there is great depth to this moment. What is a bit unfortunate though is that in post-production you have perhaps pushed this image too far.
Perhaps the biggest fault is that you have blown out her face; as a result our eyes are drawn to all that white, but when we get there, there is nothing to see. If you had maintained some tonality in the face though, then I think the image would be more engaging. The same also applies to the shadow areas the picture; just a little bit more detail would keep things interesting for us.
Go back to your original file and try working the image again, but this time use layers to blend in the old with the new. Don't commit to the first solution that the Computer gives you; be prepared to explore and weigh one option against another.
I hope this was a help, and keep working on your portraiture – I like the feel you are bringing to your work.
Cheers, Anthony.