Your instincts are right and I'd pass on a dealer that tries the old "paint/fabric protection" ploy...
Here's the sign of a good dealer in my book...
1. No 2nd sticker on the car unless it's a really useful dealer add on (e.g., leather seats or something truly that increases safety or value of the vehicle when you trade it).
2. Subie dealers are better than most but there are a few "turn to earn" ones to watch out for... The "#1 high volume" dealer will usually promise anything and use a "team" approach where the sales guy has a "team leader" who walks out and comes in to handle the final negotiations. That guy will be a pro and squeeze another few hundred out of your mom and you before you can blink so either avoid them or just learn the tactful words "No thanks... that's my number so thanks for your time" as you stand up. That's car-speak for I'm done and you'll get your price.
3. The evil twin to the team leader is the F&I guy in the back office. Ensure mom has her financing BEFORE you go even if Subaru's offering low interest rates. The dealer has no obligation to give you the "well qualified customer" rate they advertise.
4. The good dealer will have a veteran sales person who handles the entire deal, intentionally introduces you to the Sales Mgr AND the Service Mgr. That generally says it's a dealership where they intend to look after you after you sign.
I'm sure others have more, even-better tips, but these quick 4 will help you spot the better dealers who are the reason most folks love their Subies over the long haul.