Some have suggested that in the future, tenants who want to break the lease early will forfeit their security deposit.

Under no circumstances shall OWNER/AGENT’s acceptance of a partial payment constitute accord and satisfaction or forfeit OWNER/AGENT’s right to collect what would otherwise be the balance due, despite any endorsement, stipulation, or other statement on any check.

The lawyer she's working with said that the old buyer has forfeited rights to the house, or something to that effect, so she's back in the market for a buyer. 

You can suck it up and buy it, forfeit the earnest money and walk, or talk to them and see if they will do something about it.

I understand that would mean forfeiting a portion to a PM firm, but wouldn't it be worth it to avoid the potential headache of dealing directly with tenants?

I am not happy but I did a lit of research, phone calls, trying to get into the property etc but decided it was a safer move to forfeit my $5,000. 

I purchased the estimate, order and receipt for redemption of forfeited property.

BUT there is also a statement in some other addendum that i signed saying that "the deposit is non-refundable and will be forfeited to the lender if borrower does not close with highlands residential mortgage LTD for any reason other than denial.

If you don't have it done by that date, YOU forfeit the option to cancel the deal based on the financing and appraisal contingencies you may or may not have (see section 8 of contract). 

Do I just forfeit the money that should've been mine from 15th onward?