I read Magatsu-San's post the other day and was perplexed as well. All the other hidden Targ candidates are male... except for a few ridiculous suggestions like Cersei and Shae.
BUT...
How closely will Dany's arrival coincide with Aegon the Conqueror's? If it is to be vaguely similar then Dany and two males will suffice. But if it is to be almost an exact re-enactment, then mayhaps Dany will need one male and one female.
Could Magatsu-San be on to something here? Have we overlooked a hidden female Targaryen?
Just for the sake of being the first one to offer up a candidate and for the fact that I've not given you all any preposterous ideas in a while, I'll go first...
Arya.
1. She looks like none of her siblings. She looks like Jon. Jon might be a Targ. Therefore Arya might be a Targ.
2. Maybe the real Arya Stark was stillborn. Maybe Ned and Luwin (or maybe just Luwin under orders from Aemon) switched the stillborn with an unknown Targaryen princess in hiding.
3. The name Arya might really be Aerya... a very Targaryen sounding name.
4. Aegon's two sisters were warlike. In fact, they rode dragons into battle. Arya has already killed at least six people and ordered the deaths of dozens more.
5. Whenever Jon thought about Ygritte, he often also thought about Arya. He compared Ygritte to Arya on multiple occasions. Jon might be a Targ... so it's only natural that he feel a romantic connection to Arya.
6. We know that Jeyne Poole is now the new Arya Stark. But what if Arya Stark is not the real Arya Stark? What if the Arya we know is the second Arya (the old switched at birth ploy)? So on many levels we wonder Who is Arya? Where is Arya? Wheels within wheels...
7. Aerya Targaryen is already on the right continent to find Dany... just like her kinsman Tyraen Targaryen.