Gail’s accident happened while she and Helen are having a long-distance relationship while Helen was away for college. Immediately before that, Helen had visited several times and they were frequently in touch via phone calls and letters.
They hadn’t been drifting apart, but Gail did start to make other close friends (Bob and Lucius) which made Helen feel a little insecure, although she tried her hardest not to show it. This came at an already difficult time for Helen, who was struggling to make even passing grades because she underestimated how hard classes would be and overburdened herself with extra work. Helen was already feeling defeated concerning school stuff (although she pretended everything was fine to Gail so she wouldn’t worry/so spare her own pride) and so hearing about Gail having a great time with new awesome friends while she barely had time for any social life of her own (much less seeing other people!) made her feel pretty crappy.
For this reason, Helen was a little less than enthusiastic to meet Bob on her first visit back home. Despite herself, she was a little jealous of how much Gail gushed about him, and more than a little upset that one of the first things Gail wanted to do was hang out in a group instead of have some alone time together with her gf. Helen and Bob ended up getting in a huge fight (largely Helen’s fault) when Gail introduced them, and it took a lot of apologizing on Helen’s part (and admitting to her struggles with school/jealousy) to patch things back up afterwards.
After that Helen and Bob grudgingly became friends and eventually (at Helen’s persuasion) the trio blurred the lines of friendship during some of Helen’s later visits. 😉 I wouldn’t say either Helen or Gail “dated” Bob but they had some sort of more-than-friendly thing going on that isn’t easy to label.
After Gail’s accident, Helen and Bob had another huge fight at her funeral and didn’t speak to each other again for a long time (during which Helen had her mohawk “bad-girl” phase). When Helen graduated and moved back home, Bob reached out and they both apologized and bonded over their grief/good memories of Gail. Eventually this friendship escalated into a more physical relationship which Bob wanted to be more serious, but Helen tried to keep it casual because she wasn’t ready to get hurt again. But in time, she stopped trying to hold herself back and allowed herself to be more vulnerable and reliable, and after two years of going steady they got married. (And assuming you’ve seen the movies, you know the rest!)