Using Miles for someone else

Hi,
I keep seeing mentions of people using their miles, or Virgin CC upgrade voucher to upgrade someone else. I cannot find any real information on this though.
I'm wondering - if I should be splitting my efforts in gaining miles (through clubcard points, purchases, topcashback) between both mine and my OH FC accounts, or if I should just work on one?
Some questions that spring to mind...
1. Can I buy my OH a reward flight using my miles? (Without having to pay to transfer them to her account?)
2. Can I use my miles to upgrade her cash ticket?
3. Can I use my miles to upgrade a reward flight she purchased using her miles?
I'm sure there are a load more scenarios like this - what is best? What do you guys and girls do?
Thanks again!
I keep seeing mentions of people using their miles, or Virgin CC upgrade voucher to upgrade someone else. I cannot find any real information on this though.
I'm wondering - if I should be splitting my efforts in gaining miles (through clubcard points, purchases, topcashback) between both mine and my OH FC accounts, or if I should just work on one?
Some questions that spring to mind...
1. Can I buy my OH a reward flight using my miles? (Without having to pay to transfer them to her account?)
2. Can I use my miles to upgrade her cash ticket?
3. Can I use my miles to upgrade a reward flight she purchased using her miles?
I'm sure there are a load more scenarios like this - what is best? What do you guys and girls do?
Thanks again!