I'm sorry, but the deadline has already passed for applications. It closed on the 27th of March (2 days ago) according to the GSOC timeline
https://developers.google.com/open-source/gsoc/timeline. I do note that Django's own timeline mentions April 3rd being the deadline, but I'm not entirely sure that's accurate
https://code.djangoproject.com/wiki/SummerOfCode2018.
That said, I'm unsure if work on the Django Girls website would be eligible for the Django GSOC program, so I won't comment too much on eligibility in that regard. Perhaps someone else can.
As far as the work itself though, without seeing a timeline of what needs to be done or familiarity with the particular issue you're looking at, it's hard to say if the feature would be "big enough" for a 12 week development cycle. You'd also need to find a mentor that was willing to sponsor the application. It might make sense to look at adding someone from the django girls organisation that was also a django software foundation member to the list of mentors if it was decided that django girls was in scope. I think that's something we should address in future years one way or another.
To answer your question specifically though - I don't think your proposal is going to happen this year, mostly due to timelines. I'm happy to be corrected by others though.
Regards,