Here are some of the ways to beat each of the Shoujo Attack! demo levels:
Level 1: Meet the Shoujo!
Hopefully you can all figure this one out...

Basically, just use samurais/cats/demons to free the shoujos from the room they come out in, and use a chef to build a bridge to the goal.
Level 2: A Happy Demon
This level caused more problems for players than I thought it would. While freeing the shoujos on the right is easy (just claw through the wall that blocks them from the stairs and then claw through the wall in front of the goal), it's tougher to figure out how to save the shoujos on the left. To save everyone, you need to wait for a shoujo on the right to hit the wall and then turn around. Make her a happy shoujo so she jumps onto the ledge/ramp. When she gets near the left side of the ledge, make her a demon. She will blast a diagonal tunnel though the terrain which the shoujos on the left can walk up. Use a demon or cat to give those shoujos access to the tunnel, and then use cats to free everyone like explained above.
Level 3: Greenthumb
This level has two main solutions - one of them only requires 3 skills! The long solution is to turn a shoujo into a ninja as she's walking left. When she reaches the pits, make her plant flowers across them. Next, either use a samurai to clear the left or right wall. If you clear the left wall, you'll need to use more flower shoujos to get everyone up the bottom ledge. (This is easier if you let the ninja do it first.)
Alternate simple solution:
Have the first shoujo samurai-slash through the right wall. Make the second shoujo do fanservice to delay her. After the first shoujo falls, make her a flower shoujo to get across to the goal.
Level 4: The Grand Cavern
I love the music on this level! Thanks again to Helen Trevillion for letting me use her tunes

I think some people thought this level was harder than level 6. Make a happy shoujo jump over the small metal wall on the left. She needs to land on the ledge on the left side of the screen! When she turns around and is walking right, make her a chef. Have her walk over the bridge she made and fall on the land below. (NOTE: You might have to interrupt her cooking with a fanservice skill if the bridge is getting too long!) On the bottom land, have her cook more noodle-bridges until they run into the terrain hanging down. Have her claw through that. She should end up falling on a small piece of lower terrain. Next, have her cook more bridges across to the giant slope. When she walks all the way up the slope and is at the wall, have her claw or samurai-slash through. She should now be on the right side of the screen in a place with a lot of ramps. Just have her cook noodles across to each higher ramp, and she should be saved! Now you can use a demon to blast through the ground where the remaining shoujos are, and they should all walk over the bridges and to the goal. Whew!
Level 5: Take the Plunge!
Since level 4 was long, I'll cut to the chase: Use two demon shoujos to blast down to the triangular metal ramp. Make sure they're facing left. (This wasn't the intended solution to the level. I only realized it worked after a friend showed me!

)
Level 6: Shoujo Savior
Don't hit me!

This level frustrated the heck out of people. Use a cat to claw a hole in the steep hill, but turn her into a fanservice shoujo partway through. This keeps the shoujos from running off the top of the cliff and biting the big one. Next, make a right-facing shoujo into an angel so she flies up and hits her head on the ceiling above the rightmost ledge and falls onto it. When she turns around and is walking left, make her a chef to build a bridge partway across to the next platform, and make her happy (jump) when she is at the end of the bridge. At the end of the next platform, make her a flower shoujo. When she is about to walk off the end of the flower, make her a samurai so that she will dash across to the next platform. On the next platform, make her an angel so that when she hits her head, she will fall onto yet the next platform. From there, samurai-dash to the land on the left side. The shoujo could enter the goal now, but we don't want that yet! Turn her into a happy shoujo to make her jump across the goal and walk down into the pit. When she's facing right, make her a cat to claw through to the small ramp on the other side. From there, cook bridges all the way across. Use samurai/cat to break down the barrier between the bridges and the rest of the shoujos, but be careful not to destroy the bridge! When a shoujo is facing left on top of the bridge, make her plant two flowers as a stairway to the goal.
Alternate simple solution:
Stop the shoujo from dying by using the cat/fanservice method described above. At the left wall, make a samurai slash through. The other shoujo should walk into a pit when they get over there. Have the former samurai shoujo make a bridge across to the metal block. Plant a flower to get over the block, and cook noodles across to the goal. To get the other shoujo out of the pit and onto the bridge, plant a flower. This is easiest done if you claw though the right wall of the pit first to free up space so no shoujos will get trapped by the flower. (Make sure the shoujo stops clawing before she goes too far and falls into the void! A happy skill should work just fine for that. Since a picture is worth a thousand words, so to speak, here you go:
So, what's everyone think?

Does anyone have other solutions to the levels not mentioned here? Any tales of frustration? Please share!