Tora and Booster are outsiders trying to understand a new culture. Both are taken under someone elses' wing. I don't think it's ever been hinted at either being attracted to the other. There might have been a "their hot babes" moment when Booster and Ted (*1) met Fire and Ice but beyond that I don't think there has been anything more. To the best of my memory I can't recall him ever pranking her (Ted sort of did when he did a gag on her date with Guy) or teasing her the same way he does with Bea. Toras' not regarded as helpless but as a valued teammate that he generally seems to be open with. Likewise she seems to be pretty fond of him, leaping in to embrace him once she learns he's alive.
That's pretty much the base of their friendship until JLGL. Sure at first it seems the same as the team finds him lying in a pool of blood and Tora goes to hold his hand while he explains what's going on. She's also the only one to help him to his feet after they wake up from Maxs' mind whammy. What's most shocking is when her frustration from being dragged back into this mess comes back and Tora directs it at Booster. Coming from formally sweet Tora it's pretty nasty. Granted Superman just rudely brushed them off and Booster is annoyed that it took them two hours to respond to his distress call. (*2) Her response is the (pardon the pun) coldest of his three teammates, ironically Beas' is the least. Booster doesn't make a big deal over her remark just pointing out that he could have bleed to death.
After attempts to get help for their cause the team regroups to learn that Max has taken out their support systems. Tora's quick to pick up on the fact that Max didn't do anything to Booster. Later on she'll also note that he's the only one that can go back to his old life because he kept his disguise on. (Strange as it seems someone longed for the the life Booster has.) He mainly takes this in stride but he's obviously a little disheartened when she first states that she wants out. Throughout the title he's asked her nicely to stay with them, tried to explain why they need to work together, refused to let anyone go and then found her a safe house. What I find interesting is that Bea, the person who first got her into this, isn't the one Tora is addressing her concerns to. Bea doesn't get involved until she thinks she's leaving. Booster handles a bulk of it never getting annoyed like Cap does and tries to be understanding although Tora thinks he's being dismissive.
He's the one telling them what they need to do, trying to get them to stay on task, telling her things she doesn't want to hear. She still tries to get him to see her side instead of just leaving, like she knows he's reasonable enough to listen. And he finally does allow her to go although she never actually leaves the option was still presented.
My take on it: Toras' the sort of person you'd have to be heartless to pick on so I can't see anyone wanting to tease her like Blue and Gold usually did. (Now that I said that I bet someone will find a case when they did.) She's a very loving person that looks beyond the facade others present. Seeing past Guys' harshness and able to look past Beas' actions as a Checkmate operative to know her friend is a good person. I definitely think she was able to do the same with Booster, perhaps sensing a kinship with another person who's a fish out of water. Booster seems to soften around her and why not? At heart he is a very caring person who truly wants respect and affection.
I sort get the vibe that while he is a very touchy feely person (*3) Booster doesn't usually hug her a lot. Likely because that would send out the wrong message to others. Although I'm pretty sure that Guy and Bea would get over their overprotectiveness enough to trust his intentions. While Bea doesn't know what to think of his offer of listening Tora gets that he'll at least hear her even if she has to repeatedly make the same argument to get through to him. Without Ted it's natural that Tora could be a friendly ear and give him encouragement. With Booster being the leader he might even return the favor. I'm hoping to see that in the new title.
*1 Once Ted invited Booster, Tora and Bea to his high school reunion. While no one was "with" anyone as a date Guy automatically assumes Ted was trying to steal Tora when he hears about it. Most likely because the two argued a lot but it never even enters his head that Booster might be a threat. Interesting because I always assumed Booster was the best looking guy on the team.
*2 Booster has a good reason to complain, along with Captain Atoms' deduction that they've been knocked out for a couple hours that means Booster has been lying there for four hours. If his injuries were worse he would have bleed to death.
*3 Seriously have you noticed how often he touches people? Ted and him are always hanging off each others' shoulder, he causally touches a lot of people he's bonding with, gives handshakes and hugs. Other than the few touches in JLGL and the hug in Blue Beetle I can't recall them touching.