Probably fine, especially because she's likely to start laying fairly soon.
The only special thing about layer feed is that it has more calcium than feeds for non-laying chickens.
If a chicken eats more calcium than they need, for an extended amount of time, it can cause problems. People argue about how much is too much, how long is too long, and how common the problems are.
An option that's fairly popular for mixed-age flocks:
Feed chick starter or grower, which is fine for chickens of all ages.
Just keep oyster shell available in a separate dish as a calcium source. Chickens are usually good at eating the right amount of oyster shell, so this is an easy way to deal with birds that need different amounts of calcium.
In your particular case, given what you've described, I would probably use layer feed for all of them at this time.