Yaya dilema

My daughters yaya left friday last week, supposedly for a weekend vacation, she has to go to the province to visit her daughter who just gave birth. So understandbly, I allowed her to go on the condition that she should be back by Monday evening. It's already tuesday and normally it wouldnt bother me much if she extend for another day. But what really makes me mad is that I called her yesterday to ask where to send the money for her fare back. I already gave her her salary plus additional 500 for her fare back, but ofcourse she must have spent it already. So again, i dint get mad if she ask for additional since I can deduct that from her next months salary. So I called her phone, (the phone that I lend her) so technically its still mine. I just let her use it so that I can communicate with her, from time to time to ask about my daughter. I let her took it to the province so that I can still communicate with her. So back to my story, I got really mad when some guy answers the phone. So its
a. somebody borrowed the phone from her, which is also wrong, since I specifically let her bring that phone so that we can contact her, so how can we talk to her if the phone is not woth her!
b. somebody stole it from her? but I dont think this is possible since she just texted us last sunday to ask for he money.
c. she sold the phone to sombeody else because she doesnt have any intention of coming back.

Its wrong in so many ways.
1. Its not her phone, to give, to lend or to sell.
2. She could have just told us that she doesnt have any intention of coming back.
3. We were so nice to her, so nice. We let her bring her child and stay with us when she asked us to. We even send her kid to school. And I just gave her a salaary increase. I am the one who brings and fetch my daughter to/from school. As soon as I came home, Im the one who attends to my daughters need.

My daughter is really nice, she can take care of herself already. She preapares her own milk. Eats on her own. Goes to the bathroom on her own. Actually she doesnt need much of caring.

Why do we always get yaya like them this is her 10th yaya already in 3 years. This is the 3rd time that the yaya took the cellphone too. I really hate them. Now, I'm thinking if I should get another one. It would be really hard for me to dop all the chores, but it can be done. Just a little more effort on my part. I will just hire a labndera for the laundry. My cousin can look after Jea twice a week. I think I can do this. I'm sick and tired of all those Yaya who thinks their god's gift to mommies. I can live without them, Jea can live without them. I just have to plan her days when she's out of school and give it to my cousin before I live so that she will still have a productive day. I just hope my cousin would say ok if I ask her to stay with Jea for 2days a week.