I.D.
S., at this age, she should not have any food at night! Her body has adjusted to eat as much as she needs during the day, especially if she was sleeping through the night for a while. If you feel like she needs something, offer her a sippy cup with water. I have 3 kids and when they all would start waking up at night like it's happening to you, they would suddenly reach a new milestone or do something new or stop something (maybe she is getting ready to stop nursing?). It was like they were getting anxious or excited about what was coming soon. I would advise to keep doing what you do, rock her, put her on bed and if she wakes up while during this, just push her mattress with your hand so she can feel the rocking motion but without you holding her...then make the movement softer and softer until you're gone. I'm so sure this will go away soon. It's always stressful to have the first child, but it gets so much easier with each more. You feel confident about what you're doing, you aren't as stressed and you enjoy them even more. The bonus is that siblings entertain and teach things to each other. And older siblings are very helpful getting you emergency wipes and diapers or anything you need handed right away!
PS Don't feel bad if she is crying if you have done everything she needs: if she is not hungry, she has a clean diaper and she's gotten enough sleep and attention. You aren't ignoring her, sometimes kids want some extra attention or go through some insecurities so just talk to her from the doorway so she knows that she is not alone. Always wait a few minutes before rushing in. Most times they go back to sleep after 5 minutes of crying. And what's key...you won't start a new habit (rocking at midnight, sleeping with you, eating at night, etc) and that's reaaaaally hard to break (a whole new story).