1. I have some questions about Becky drinking addiction how did it start? 
And how did her family and friends feel about it
2. How did Tobey feel about it when he found out
3. This maybe be a bit of a sensitive topic but did Becky get hurt during this path 
So I kind of want to clarify what this drinking addiction looks like, but I'm trying to be very careful about how I word this because I don't want to imply that just because it doesn't look like what most of us think of when we think of this, doesn't mean it isn't a problem.
Like I've stated previously, this is a case of high functioning alcoholism, she's still excelling at her job, she's still going above and beyond as a mother, there are no financial issues because of this, she's never been black out drunk and frankly, she's only ever gotten drunk a handful of times in her life. It's hard to detect, but that doesn't make having a drink to unwind every night or every time you have to face something that upsets you a healthy thing to do, physically or mentally. If you've seen the show Bob's Burgers (and if you haven't, go watch lol, it's one of my favorites), I'd say she's like a step up from Linda Belcher? I'm not sure if that's even a good way to explain it but that's the best I have.
To answer your questions.
Earliest instance of this was when she was 16. The exact event may change, but currently the idea is that her friends threw her a 16th birthday party (thinking the one the Botsfords threw for her was fine, but kinda lame for a sweet 16), and someone, unbeknownst to her friends, spikes the punched. Becky went to get a drink, and could tell immediately, and she did think about dumping it out and walking away, but this party was for her birthday, her birthday that had sucked because of Wordgirl (like many other birthdays she'd had), and frankly, it had just been one of her worst Becky vs Wordgirl weeks and she had been extremely stressed out. For these reasons, rather than throwing the punch out, she rationalized that she'd earn the right to try drinking, and because she had no experience with alcohol, and was young, and didn't know her own limits, this was the first of few times she did actually get drunk.
As for how her friends and family reacted to this specifically (I'll go more in depth with who knows what overall in a minute), her friends, which as the time were Violet, Scoops and Tobey, basically went "oh shit..." when they saw Becky and she drunkenly told them what happened and what her thought process was. They all acted immediately, Tobey got her home, Violet got rid of the spiked punch, and Scoops did a little investigation to figure out 1. if anyone else was drunk 2. who exactly who had spiked it in the first place. By this point, Bob had left years prior, so he wasn't around for this, which in some ways is a good thing, because he would not have handled it with the same grace that the Botsford family handled it. Bob would have lectured her, but when Tobey dropped her off and explained what happened, Tim and Sally, being the best damn parents that they are, handled it without judgement. Tj, seeing his sister in this state was horrified, but did nothing but listen to what his parents told him to do.
When Becky was sober, Tim and Sally asked her what had happened and what was going through her mind, and stated she wasn't in trouble, they just wanted to help. By this point, Becky had told her family she was Wordgirl, so she didn't have to lie, and was completely open about how extra tough and stressful her life had been that week, largely because of Wordgirl. Tim and Sally were quick to act, they told her that some of the smaller villains Wordgirl needed to stop battling and let the police handle it. For example, there was no need for Becky to get in trouble for ditching class because of Amazing Rope Guy. They also insisted that Becky start taking easier classes, even though she was perfectly academically capable of the more advanced classes, so she'd have a lighter workload. The one exception to that probably would have been any reading or literature classes, simply because she did actually need to be challenged in those areas. They also completely rearranged the household chore duties, mostly giving Becky chores that were extremely flexible in when they needed to be done, so she didn't have that pressure on top of anything else, and this was a good example of Tj listening to his parents without question. He didn't care what chores he was doing, as long as it was something that would help Becky.
There were no more incidents like this until after Becky was legally old enough to drink, and even then they weren't necessarily as bad as this incident. Because of this, and how well Becky handled life in general, no one really questioned anything. In their 20s, Becky's friends basically watched this problem develop without ever really realizing it.
With that said, this is the current status of what everyone in Becky's life knows regarding this is:
Becky: In complete denial. How can she have a problem when she's so functional in life and nothing is effecting her family in anyway?
Theo and Julie: Completely clueless, and it's gonna stay that way.
Bob: obviously doesn't know a thing he hasn't been around...but that is going to change now that he's back.
Tobey: "Finding out" is not really the wording I would use here. It's more like over the years, he noticed patterns and pieced together that there was a problem. He's confronted Becky about these concerns, but as stated above, Becky doesn't see a problem.
Violet and Scoops: Don't know she has a problem, but do suspect it.
Becky's family: Don't know she has a problem, but wouldn't be surprised if someone told them that she does.
No, Becky hasn't and won't get hurt because of this, though there have been/will be times where feasibly something could happen, she's lucky enough that she always has people nearby who love her and can get her out of any jam she might have gotten herself in, the birthday incident being a great example.
