If one boot is larger than the other, contact them because some online stores allow free exchanges even if they don't have free return shipping. I've never even heard of those brands. Maybe you should try returning the bindings (since you're not going to use them) and exchange the boots for a pair from a different brand. The Women's Summit boot from ThirtyTwo, which specializes in boots, is a little more expensive ($120) but it is easily one of the best beginner boots money can buy. It would last a good amount of seasons, and the liners are heat-moldable.
If your Burton bindings are ok, I would return the Siren bindings (another brand I've never heard of) and the boots, then get a pair of either Burton or ThirtyTwo boots.
As for the board, Camp Seven is a brand owned by wierdsport.com. It should be ok as most people I've known have started out with a bargain brand board. I had a 5150 Stroke, which was stiff, heavy, and caught the edges all the time! So don't worry about the board.
This would result in the Burton bindings and the board you have now, with better boots that will fit both your feet and your bindings well and will last a long time.
I think it would be worth paying the return shipping, but usually if you're nice you can talk them into sending you a free return shipping label. Tell them the boots were sized incorrectly and that you haven't used them yet (clean them up with a Clorox wipe or something). Also tell them you haven't used the bindings and they should give you a refund for both.
That's my advice. You don't have to take it but if the boots are really a problem then go for it. Good luck.