Sounds good, and plenty of roost then.
Yes I'd try putting her on the roost each night (if possible, check again later in the night to see if she sticks or if she jumps off), and hope that it eventually clicks in her head to go up on her own.
5' of roost for how many birds? Have you tried physically placing her on the roost, and if so, what happens?
If it's not a physical problem with your bird, then it's possible she's being bossed off by others, even if there is roost space left to spare.