RTL-SDR for sure, don't use the junk antennas that come with them though. Use SDR# (pronounced sdr sharp) as the program recieve. If you want you can pipe the audio from SDR# into DSD+ using a virtual audio cable and then you can listen to P25, DMR, etc. It's a little bit of a learning curve at first but then it gets easy.
Could you just leave her a handheld radio so she could also monitor your communications? If you lose power or windows decides to do updates at an unopportune time you may run into issues in an emergency. Otherwise APRS world work if you're able to get into an I-Gate. You would have to guaranty an internet connection for her to be able to reach WWW.APRS.FI . Alternatively you could setup a basestation to receive the APRS packets directly but now you're back to square one and needing a computer powered up and connected to the radios. I suggest either getting her a handheld scanner or giving her a handheld radio and just contacting her direct through whatever service you're both capable of operating on (Amateur, FRS, GMRS, ect.)