Samsung Galaxy S3 bootloop

[regrebel]

Hi, unfortunately my mom's Galaxy S3 has finally started dying some weeks ago, first losing text messages and now, just yesterday, getting stuck in a bootloop. I am posting a new thread because, even though I've been up pretty much all night trying to figure this out both by myself and with other forum threads, I have not been able to find a solution either myself or on a forum. The phone does charge and show the battery charging image, and it can get to both download and recovery mode; however it refuses to boot in safe mode, clearing cache did nothing from the stock recovery and I cannot flash a custom one since the bootloader is locked (this phone is all stock and unmeddled with, it was only used by a 60 year old woman). Now, the problem is: I would factory reset it but my mom CANNOT afford to lose her contacts and memos, she would probably get fired or something because they are extremely important.
I would love to solve this problem for her since it's mother's day too
Thank you very much for your time and I hope you can help me.

 

[smvim]

You referred to flashing a custom ROM but I'd suggest a better option (in your Mom's situation) is to flash a stock ROM. (Custom ROMs being an issue with a locked bootloader, stock should work whether locked or not.)
Since you can get into both Recovery or Download Modes things aren't completely bad, using Odin (or the Open Source equivalent, Heimdall) to flash a stock ROM, the /data partition, where all her personal data is stored, should be remain as is. (Well unless there's a problem but at this stage your options are limited.)
Get the ROM that's specifically for her particular model of S3, try sammobile or updato. Both sites are reliable sources for Samsung stock ROMs (sammobile intentionally restricts its download servers so even if you have a fast connection on your end, don't be surprised it's a slow download).
sammobile
https://www.sammobile.com/firmwares/search/galaxy s III/
updato
Download Firmware – Samsung Update

Regarding her contacts and memos, and whatever else, it should be obvious now that setting up a good backup solution needed to be done beforehand, not after the fact. If her Contacts were set up to sync with whichever email service she's using than hopefully there's that to fall back to. But once you get her phone working again, use something like Google Photos to get her photo library auto-archived up into her online Google account. Use apps for services like Google Drive, or Microsoft's OneDrive, or Dropbox so her files and miscellaneous items get auto-backed up somewhere.
If she's not comfortable having her data stored online, than set up a backup solution to a local computer. Smartphones simply cannot be relied upon as a single source, archive.