on the cheap

Simple way to connect a streamer to a receiver with Bluetooth is the Audio Engine B1 Connect via RCA and it also connects flawlessly to your phone 

+6 for any WiiM product. The WiiM Mini (hockey puck design) is reputed to have a "thicker, darker sound" than the WiiM Pro or Pro Plus so I'd choose one of those instead and call it a day. The great thing about the WiiM's are their software. So easy to use.  No matter how good something is, if the user interface sucks and is aggravating to use, you simply won't use it. 

I've read some stories on this forum about some relatively expensive streamers that have piss poor software.  That WiiM can go head-to-head with BlueOS on useability is a great selling point. 

There are rumors that WiiM is coming out with yet another "better" streamer, but what it will be, and when it will be out, is anyone's guess. 

If she doesn't have an amp, you might want to look at the WiiM Amp, which has the streamer built-in.  The WiiM Amp has these features:

• analog stereo line-level RCA input (for a CD player maybe)
• optical digital input (for a CD player maybe)
• HDMI ARC port for a compatible TV (if this is important to her)
• USB Type-A input for connecting an external drive loaded with music (you could load up a drive with CD rips for her).

I wouldn't be embarrassed to use a WiiM Pro Plus to feed say up to a Denafrips Ares II 12th DAC and think I was getting about as much out of the Ares as you can get. 

But of course, for your sister, you can get by with the WiiM Pro Plus just fine. 

I own 3 WIIMS and in my experience they are great if you are using them to output s/pdif into a better external dac.

I did not like the sound from their analog outputs...

Don't know why anybody would want to stream their sister...just call once and a while maybe...

@wolf_garcia " streamer for my sister."

i have no idea what you are talking about