The woman become aware of several unknown persons following her on pushbikes.
The offenders knocked her over, and assaulted her by kicking and punching her, causing cuts to her head and bruising to her hips.
During the assault, the offenders attempted - unsuccessfully - to take her mobile phone.
Following the appearance of an unknown vehicle on the A16, the offenders ran off in a direction not seen by victim.
A Lincolnshire Police spokesperson said: “This was clearly a very frightening ordeal for the victim and will be of concern to the community.
“We would like to be clear that the victim believes this to be an attempted robbery. There is no evidence or suggestion of sexual assault.
“We will investigate meticulously any evidence that comes to light and would like to urge anyone with information to come forward.
“We would specifically like to speak with the driver of the vehicle that passed at the time, causing the offenders to flee.”
If you have any information to assist the investigation, call Lincolnshire Police on 101 and quote incident number 221 of April 8.
You can also email [email protected], or report the incident anonymously via CrimeStoppers on 0800 555 111 or https://crimestoppers-uk.org.