She looks very pregnant. Rats can mate in the blink of an eye unfortunately.
Any chance you can get your males neutered so this can't happen again?
As far as rehoming, you may want to contact Rattie Tattie Rescue to see if they can help you or at the very least do a courtesy posting. You should try to screen adopters and charge a small adoption fee. You should only adopt out same sex rats to same sex households (unless they are altered) so that your rats' babies aren't bred again continuing this cycle.
If you're 100% sure that the day your rats got out at the same time is the only time they had contact you can hold out, but otherwise I would move her to the bin cage soon so there is no chance of her giving birth in her regular cage and having the babies get injured.
What are you feeding for a regular diet? Also, legumes (cooked, of course) and beans are also a good source of protein.
For the birthing bin, no hammocks or anything they could fall from or get crushed by.