Aliens have invaded the earth...

[Strinder]

Read it in high school a long ways back. The parts I remember in no real order are.

1. The war is essentially over, aliens have won and have taken over the earth.
2. The offenders have three toes on their feet that we learn when one takes off her boots to push a boat into a river.
3. Human resistance fighters capture one of the Leaders of the Aliens just before another group of aliens (diffrent species) show up and start attacking the earth due to its "strategic importance".
4. A teen in the resistance is somehow paired up with the daughter of the leader that was captured by the resistance.
5. The daughter of the leader has rank in the alien command structure only because her father does and his loss down rates her in the society.
6. The kidnapping of the leader is no real loss to the aliens and they just put another in charge and continue as usual, foiling the attempt to use him as leverage.
7. The second batch of aliens that show up are very thin.

And that's about it. Been trying to find it for a few weeks but I realize its not much to go on. Thanks in advance.

 

[CassFrank]

Possibly Pamela Service’s Under Alien Stars (1990). The invasion is over, aliens have three fingers and toes, human teen teams up with alien, and there is a skinny invading race that resembles Swiss Army knives.

After conquering Earth ten years ago, the Tsorians use it as a military base--with opposition from the Resisters. When the Hykzoi threaten both humans and Tsorians, the two groups must put aside their hostilities and unite against the common foe. A fast-paced . . . adventure with deft characterizations and an exciting plot.--Booklist.