To add new peds, use fastman's limit adjuster plugin.

Here is a tutorial:

https://www.youtube.com/watch?v=KSzGUf1qMMo&ab_channel=WhamDieMoe

Add this line into peds.ide file.

***, SBFYST2, SBFYST2, CIVFEMALE, STAT_STREET_GIRL, woman, 1007, 1, null, 6, 1, PED_TYPE_GEN, VOICE_GEN_HFYST, VOICE_GEN_HFYST
***, DWFYLC3, DWFYLC3, CIVFEMALE, STAT_STREET_GIRL, woman, 1980, 0, null, 6, 2, PED_TYPE_GEN, VOICE_GEN_DWFYLC2, VOICE_GEN_DWFYLC2

Don't forget to enter ID you want ped to have.