Of course, you could buy a ticket with her 10K before the end of May for a flight in the coming months. The ticket will have a year vailidy, but miles cannot be recredited if you sdon't use it. Of course, there are few tickets for that price.

I find the transfer by points.com quite expensive; 120EUR for 10K miles is not a bargain.

Once miles are transferred to your account, the validity will be dictated by your account. All miles in an account have the same expiry date and depends on when you take a flight on ST. Transferring miles does not extend the validity of your miles but there is no specific expiry date for specific miles. At least that's my reading.