Yes, she can transfer now. It's called 'gift of love' for taxation purposes and should be tax free. Properties too as they are transferred and not being sold, so no RPGT applicable.

While transferring property and inheritance while someone is still alive is a way to avoid inheritance tax, Malaysia still doesn't have this form of taxation. However, transferring away properties while still alive does alter family dynamics and relationship. So do consider that.

Best course of action is for your mom to ask all siblings (and their partners) to come attend a meeting so all this can be discussed in open and any objections / dissatisfactions can be heard.

Transferring is surely cheaper than will. Will involve writing the will, custody of the will, executing it with court probate...