Is what happened between the questioner and her two female colleagues considered abandonment, and what is the correct action in each case to avoid abandonment?

The Shari'ah forbids estrangement and abandonment among Muslims for more than three [days]. The majority of scholars hold that abandonment ceases with a mere greeting (salam), and it is not a condition to deliberately seek out one's brother to greet him; rather, what is required is to greet him if they meet. Your not meeting the aforementioned girl is not a forbidden abandonment. As for the other girl, if you meet her with others and greet everyone, then you have fulfilled your obligation. If you meet her alone, do not neglect to greet her unless there is harm to your religion or worldly affairs in doing so, in which case there is no blame in abandoning her.