This is a snapshot of wards on the map on the 20th-minute mark, right after Secret won a fight close to the Radiant T2 mid tower. As you can see, they have vision covering almost all of the radiant jungle (as well as vision on Rosh), most importantly the two jungle high grounds that Medusa uses to flash-farm. This gives them an opportunity to continue applying pressure and finding gank opportunities, as well as to continue controlling Roshan.
Medusa loves static, clean 5-man fights. She loves standing in front of her allies where her ultimate and tankiness make it very hard for the enemy team to initiate.
The right way to force such engagements is to push as 5 – your opponents will be forced to take the fight to defend their towers (or lose them without contesting).