How can taylor swift re record songs?

I'm so confused. My sister was telling me about how Taylor swift is re recording her old music because scooter Braun owns her old music and she wants to have sole ownership over it.

So how can she release similar or exact copies of songs she doesn't own but other artist constantly have legal battles for having songs that have some similarities to it? Like Ice Ice Baby for example. Is she not violating copy right laws by doing this?

Edit: good news. I get it now!