I just picked up a BLU Win HD 5 for $95 refurb to use as a music player, backup/overseas phone, offline GPS, etc. and I must say I'm pretty impressed. Is it as nice as my company S5, well no, but even the non-refurbs are 1/5th the cost off that.
The build quality is quite good, 1Gb of RAM is plenty for WP 8.1, haven't encountered any slowdowns or hiccups. Battery life is very good with the caveat that I don't have service to this phone, just Wifi. This weekend it was fully charged in the morning then I used it to read email, browse the web, read the news, install some apps, track a 3.5 mile walk with my dog, play around with some videos, read on the Kindle app, and then stream music while hooked up to a Bluetooth speaker for 3 hours (with the screen on for a large chunk of that time) and still had about 30% battery remaining. It comes with screen protectors and a simple gel case, which will be good for your niece. The phone itself is slim and light but not too light and looks rather good. The screen is crisp with good colors.
The big con would be the camera. Some of the Amazon reviews said the pics would be real washed out and they are. Pics I took with a digital camera on my honeymoon 12 years ago look better. Other than that the only other thing is sometimes the screen a little too responsive with swipes being interpreted as presses. Oh and this is the non-LTE version. Since I won't really use this much as a phone except for traveling to places like Aruba (where the offline maps can be handy) I wasn't worried about paying the extra for the LTE version.
Even though i can't speak to call quality, I hope this helps. I'd say from what I experienced so far, getting a Blu as a reasonably priced phone would not be a bad choice.
This is the one I got:
http://www.amazon.com/gp/product/B00NQGFQ7C/ref=olp_product_details?ie=UTF8&me=