Ref. No. 2264/44-2418
In the name of Allah the most Gracious the most mMerciful
The answer to your question is as follows:
If one wants to marry someone, then there is no harm in supplicating for her\him and one can supplicate Allah Ta'ala for the said purpose. However, one is not allowed to talk to a stranger man or to a stranger woman before marriage. Just being engaged does not eliminate the strangeness.
And Allah knows best
Darul Uloom Waqf Deoband