The 63-year-old had just reached her East Sussex home in the early hours of Saturday morning, when she was approached by a cyclist who she chatted to briefly.
However hours later the man returned and broke into her home, where he crept into her bedroom and assaulted her.
Police are now hunting for the man responsible for the assault, and are appealing for witnesses in the area.
A spokesman for Sussex Police said:
"A 63-year-old woman was walking home with her bike up West Hill Road in St Leonards, East Sussex, in the early hours of Saturday morning when she was approached by a man on a bike. They had a very brief chat before the woman continued home.
"She went to bed, however woke about 3.45am to a man in her bedroom and being touched. She managed to push him away and raise the alarm with her neighbours, who called the police."
Detective inspector Gavin Patch, of Sussex Police, said:
"This was an extremely distressing incident for the woman and is a very unusual type of sexual assault. "Police will be patrolling the area to speak to anyone who has concerns and making enquiries about the offence."