But of course, you can have 3 healthy plants too...
Shake the soil off, pull the roots gently apart; try to find the plant/roots which has the least resistance, the one which allows you to pull the fine filaments away. Try to untangle the roots very gently. If this is still not successful, rinse the soil completely, and you'll be able to pull the roots apart very easily. Don't worry about the eventually tearing filaments; as they break, they'll stimulate more vegetative growth.
Two days ago I separated over 50 similar plants which were overwintered, but still small (late plants; they couldn't grow because the lack of light/soil). Most of them are 15-20 cm tall despite of their age, and they are doing fine. They got their new big pots and they immediately started to develop fresh tiny leaves. I foliar feed them with a bionutes after transplanting.