1st, buy a fisher price flashlight. It stays in the big girl bed. They are be best out there on battery use. They don't stay on a long time. You turn them on and after a few minutes they fade out. It takes a single push of the button to get it back to full power. She will love the power it gives her to turn the light on any time she wants it. I tried some of the others but they are not near as user friendly.
2nd, I would buy her a bed buddy. Something about her size to snuggle with or something special she really likes. She can only use it in her bed. Let her pick it out. Make it a bedtime ritual to put the buddy to bed in the big girl bed.
3rd, give her a choice of sleeping with the buddy or on the floor next to your bed. You can still reach out and touch her and she will know you are there. After a few days you can move her to her bed after she goes to sleep and make a special breakfast if she makes it all night. After a while you can move to putting her down in her bed. Be sure to talk up how big she is. Make it a big parade to the bed, read a story, buy her a crown or whatever you think will work to make her feel big. I promised my son a pancake with chocolate chips when he started sleeping in his bed. I only put a few on there with some whipped cream and it made a big difference.
Maybe you can find a fun bedspread to put on her bed after she starts sleeping in her big bed. Maybe buy her the little polly pockets or whatever the things she likes are and give them to her every few days. Put one on the table and tell her I would like to give you this pony but you have to sleep in your big girl bed all night.
Finally, you have to remain committed to putting her back to bed there for several days. It will not be easy and yes, you will be majorly tired but in the end it will be worth it. Say something like, I am so proud of you. It is still nighttime and you need to go back to your big girl bed. Let me walk with you. Then you walk her back to bed and tuck her in. I wouldn't get into long debates with her about it, just tell her what you expect and prepare for the battle. After a few days, it will get better but if you give in it will get worse, much worse. then any progress you have made will take three times as long to get back to. Basically your options may boil down to a week or two of exhaustion or taking the long way home adn giving in before you know where you went wrong.
I just hope that you don't let the new one sleep with you. It seems easier in the beginning but in the long run it will be easier to scoot a bassinett or playpen next to the bed. I tell my friends that if you let the baby sleep with you, it is really cold in that bed when you decide to kick them out and they don't want to go.
Good luck
C.