is facebook enough evidence for small claim court?

[7againstThebes]

Facebook posts are sufficient, as long as you can prove (reasonably) that the facebook posts came from the person you claim. Here's what you have: you have an agreement with an agent (the midwife) for the sale of your vehicle. Your agent represented that she has a buyer (cousin) at a set price ($11,000). You agreed to the sale price. That's the first contract.

Your second contract is between the midwife in her capacity as a guarantor of the first contract. With the evidence you have, you can certainly bring your claim to enforce the agreements, both the sale contract and the guarantee.