Mechanics living up to bad reputation

ok so here is the situation I came across while getting some gas a couple days ago. I see another e46 at the station with the hood up and a confused looking (and hot) girl staring under it and then I see a sin being commited when she starts pouring green coolant in. I am about to ask her what is wrong when she jumps in and leaves . I go in to get my change and she is already back with hood up. Anyways after talking to her I find out that she had just picked up the car after having entire cooling system replaced and had taken it to an America's Tire. I was thinking oh dear god, when she said Americas Tire. Backstory on car is that it did overheat severely before getting fixed but they told her it would be fine if she replaced entire cooling system for a price of $1100. I asked if they mentioned the possibility of a blown head gasket and she said no. In my opinion they knew or should have tested for a blown head gasket before charging her the money to fix cooling system but they made critical mistake which I believe will hold them liable for replacing entire engine in this 330i. When she picked it up it was leaking and she went right back, (sensor in lower hose o-ring) they tried to half ass fix it and put a ton of silicon around sensor in new hose to stop leaking and gave her the car. It made it for about half an hour before it shot entire sensor out of the hose and dumped the coolant and overheated again. I told her to call a tow truck and when she was ready to take it after the holiday to call me to go along. This is a clear example of them taking advantage o someone who does not know any better, They should have been honest and told her about blown head instead of replacing cooling system and make a few bucks, but their silicon patching job may cost them. I told her to say that car never overheated before she took it to them for a leak repair but it did overheat on freeway today after they worked on it and then show the silicon that failed and that's there fault at this point. I am in school to hopefully work for bmw and am sick of dishonest people in this industry giving all of it a bad name. I would like opinions on the situation from everyone including if you think im right the head gasket was blown before going to shop, (she said it was into red for a long time multiple times) and if you think shop is now liable considering they told her car was fine and would be fixed once they did the work. Also I don't think its related but she said prior to the car starting to overheat that the red oil pressure light would start to flicker but oil is not low and no strange noises. Probably faulty oil level sensor im guessing. Sorry if this is a novel of a post but I wanted to share this with everyone.