- Bála bych se. - I (fem.) would be afraid. - by+jsem+se -> bych se
- Bála by ses. - You (fem.) would be afraid. - by+jsi+se -> by ses
- Bála by se. - She would be afraid. - by+se -> by se (no contraction here)
These contractions ("bych se" and "by ses") are the only way in standard Czech. Some native speakers, however, wrongly believe that they are colloquial/non-standard, and wrongly write these conditionals uncontracted (e.g. "by jsi se" - incorrect).
For comparison, note a non-reflexive verb, such as "hrát" (to play):
- Hrála bych. - I (fem.) would play.
- Hrála bys. - You (fem.) would play.
- Hrála by. - She would play.