I think she feels bad about you interrupting her serious work. It's like when we do stuff we really like. We don't want to make a mistake and mess it up. So I can understand how frustrated she must feel when someone else does it for her.

It's best you give her some time to think. But let her know in humble ways that you're really sorry. Sometimes explaining stuff can come across as you hurriedly trying to fix the problem. She wants you to know that you really hurt her feelings. And that's okay.

Stuff like this will pass in time. But you have to find ways to show that you care about what you did. Say sorry every now and then. Not too much or too often. And when you do apologize, always be sincere, succinct, and polite. Never drag it out to another explanation.

And if she does ask you why you did it, calmly explain how you felt inclined to help her. And that you recognize that your good intention doesn't make up for what you did to her hard work.