If I were the OP I would never use the OTA again. But thank goodness she has been made whole. Rebook and use a real travel agent who stands behind their actions.I understand what @Enot is requesting.....it is not cut and dry BUT if a traditional TA cancelled the remaining tickets even though the client only requested one ticket to be cancelled, the TA would be obligated to get their clients to their destination on the TA's dime. Just because the TA is essentially a ticket broker should not exempt them from doing the right thing.
If I were in the OP's shoes, I would be reticent to purchase new tickets to the vacation destination without any guarantee from the OTA that they would be reimbursed.
In the end, this is a losing battle based on the fact that the OP has been made whole on their original tickets and only (I use this word this hesitantly) lost out on their vacation but did not suffer any financial loss.
@Enot my guess is the only chance you will have receiving something is if you ask for travel vouchers, not cash. Even then, it is not likely you will receive anything.
The conclusion: OTAs suck!!!