This is another one of those (many) times when the FA demonstrate how much of an amateur operation they are. The rules haven't been updated on their website etc, but they've been amended by press releases (like the top team and best runners up go through) and in emails sent this week to the clubs (saying that best runners-up will be based on "average points per game" - because some groups have 3 teams not 4). Personally, I find it immensely disrespectful towards the clubs, the fans and the journalists covering the game - but apparently that's because complaining United fans are just newbies, who contributed nothing to the development of the women's game and should be more patient with the bold pioneers who run it and have to make up the rules as they go along
On top spot, I believe it's GD that decides position (same as last year), so we've no guarantee of qualifying even if we win our last two games. We need good margins as well as wins. City currently have a GD of +5 to our -2. If we come second, as far as I can tell looking at the other groups, it's unlikely that we go through as a best runner-up as our GD won't be good enough.