You may be better off waiting for some natural appreciation unless you think you can get a much higher appraisal or much lower rate.

I did this 10 months after purchasing the property and the home appraised for 45k more afterwards.  

Using the FHA 203k loan, you could build out the ADU assuming it appraises. 

She wants to get an appraisal of the land value with and without the timber.Anyone have suggestions on who she should call to determine the value? 

That $2400 figure is based on the current owner's appraised value which is ultimately derived from their original purchase price.

For my particular situation I have the funds to provide the deposit in Cash and had a pre-approval letter from a private lender for this property (which is dependent on appraisal, title, and final underwriting decision), but am unsure if they will accept this as documentation or if I will be out my earnest deposit if I go for this opportunity.

Did a (partial) cash-out-Refinance with the house being appraised at 180k.

I had a couple of questions about the appraisal process, particularly about renegotiating the seller's concessions if the appraisal comes back low.

I want to know how do appraisers come up with comps and ARV.

You could increase the purchase price, assuming the appraisal value supports the higher price, and have the seller contribute the delta towards your UFPMI.