In late Victorian London, (1880-1900ish) many poor women turned to
prostitution or were sent to workhouses. Excluding these options and
marriage, what options were available to poor and uneducated women?

Convents?

Service - working as skivvies, maids, cooks etc

Also wet nurses (if appropriate), nursery maids, (junior) nannies.

Also plenty of factory jobs - matches come to mind

Like Eliza, sell flowers.

The sweat shops of the rag trade.

Chorus girls.