Anyone can share if its feasible for a 28 yo to wipe out her CPF OA acc to service a mortgage loan? Will be looking to buy a 1br freehold condo?

It depends.

Depends on how financial literate you're in terms of personal finance.

If you're generating a higher returns in your investment using cash, you'll want to use as much CPF as possible to pay for your property plans.

If your cash returns is lower than CPF return of 2.5%, Use CASH.

If you feel that you want to max out your CPF Returns by transferring it to Special Account, then Use Cash.

Therefore, it's up to how financial savvy you're in personal finance plans.