To echo some of what others said here - relatives who live a half a country away are strangers. Truly they don't know you - even if you feel like you know them since you've known about them since birth. Think of when you were age 17-18 and an aunt who you rarely see came to visit - I would venture to bet that you probably only said hi, gave a hug and went your own way. In addition - it was graduation weekend I assume and there were probably parties that she wanted to attend of various friends who've also graduated that she has grown up with and attended school with.
All that being said, both neices should not be rude to you or their grandparents - there should have been some expectation that they spend a meal or a few meals together with you (depending on how long you were there). As for the texting - we have established certain times as phone/text free times - such as meals and family celelbrations. If the kids are having a hard time following those guideline we help by taking the ph one away for a period of time - sometimes just for that dinner, sometimes for a few hours, sometimes a day or 2 or 3. all depends on their will & attitude.
Finally - teenagers are different than any other creatures on earth. Their job during this era is to separate from their parents - they generally seem way too willing to do so! I've had situations with my almost 15 yr old daughter that I would never have imagined would take place. She's been fresh and rebellious while only a short 18 months ago I was her best friend. So we discipline, we take away priviledges, we ground, etc. And it works until the next thing comes up. My dear daughter - who can be such a pleasure at times told me last night that she's a teenager and she's "supposed to try to sneak out of the house, and she's supposed to try to get drunk, etc." and I responded that as parents then we're supposed to put up boundaraies and discipline when the teenager tries these tricks. ;o) <deep sigh>
When my kids were young like yours I was shocked at what was considered OK behavior by my sisters & brothers as it regarded their teen kids - then my kids reached the teen years and I'm finding I have to take most of it back. ;o) !!!
Generally we do the best we can.