If it's gas, it will pass, and you got lots of good suggestions to help.
Also be sure she is fed to capacity all day every day as well as before bed so you know she's not hungry. Do a nice soothing bedtime routine, and then, especially since you think she's not in pain, don't console her during the crying spell if you don't want it to develop into a necessary habit. She will adjust to soothing herself to sleep over time.
There is a normal "45 Minute Friend" that strikes babies, where they wake up crying about 45 minutes after you put them down. This may be what's happening. It is common and normal. Just let her be, she will go back to sleep. Good luck!