Are there more was to stop props?
Props can be gently weaned (gradual withdrawal) or dropped cold turkey (just dropped out right). Either way you would reassure and comfort your LO through the difficulty of the change.
I think you're really at the point now where there isn't another step in a gentle wean or gradual withdrawal other than verbal reassurance from outside the room. You are already only going in for a brief time then leaving again so verbal reassurance is the next step really.
The only other option I can think of is to keep doing what you are doing which is a form of WI/WO (walk in walk out) until she out grows it. Personally I'd go for trying to break the habit and get that last bit of sleep training that needed - partly because I only have enough energy and patience for a certain number of days/weeks and then I'm exhausted so I prefer to tackle tricky times even if it means a few nights with even less sleep.
If she comes to your room you return her. First time you say "It is night time go to bed" and take her hand and take her back to bed put her in and say "go to sleep". If she gets up again you do a "silent return" where you do not speak but take her hand, guide her to bed, then leave. And repeat as needed. She'll get the message and eventually sleep.