Great advice here – I'd just add that for your own mental health, train the steps you need her to know at times when you're NOT actually eating.
So teach her 'on your bed' as a general command, not something that only happens when you're eating, and train it outside of mealtimes.
Teach her a nice strong 'stay', again, not at mealtimes.
And similarly, sit down at the table with a plate of food that you DON'T intend to eat while you train her to stay on her bed. If you're genuinely hungry and trying to eat AND train her, you'll be distracted, more easily annoyed, and it'll be harder to set her up for success 
So have some 'fake' mealtimes where you practice this stuff and you're actually fully focused on helping her understand what's required and why it's a good idea to be on her bed during those times.
Also if you ARE going to give her scraps, don't ever have those scraps coming directly from your plate. She only eats from her bowl and at her dinner times - as soon as she connects your plate or the table with something for her, you're undermining what she's learned.