I have been nothing but encouraging and supportive to my maternity leave cover, and because in part of my praise of her (my manager was unsure at first) she is now a permanent member of staff. I feel like I have created a monster.
It's hard to talk about without sounding petty, but today she emailed a plan for a presentation that I had designed absolutely (imo) making it look like her work - not cc-ing me in but making me a recipient 
I am a mug. I am open about what I am working on, always always credit people's ideas. I just don't know how to handle her and I feel really upset.
So, how can I make it clear to those to whom it matters that it is MY work without lookig petty. And how can I get tougher in future?