Lilly was very young when Matthew became friends with her father, and as their friendship and his attachment to the Teal family grew, she too grew increasingly more attached to her 'uncle'. After she was orphaned, her uncle and aunt worried about being able to afford her, but Matthew intervened and took her in 'as per Johnathan's wishes', much to her aunt's displeasure.
As her guardian, Matthew dotes on Lilly as if she was his own, and is extremely protective of her. In return she absolutely adores him, and makes every effort to make his life as comfortable and loved as he has made hers. In her eyes he can do no wrong, especially since the darker and more violent aspects of his past and nature are firmly hidden away from her. Every positive, lawful step he has taken in his later years has been to distance himself from anything that could harm her.
Being the only one of his brothers not very physically inclined and more interested in sitting inside and reading or tinkering, Darryl got along well with his cousin from childhood and spent the most time with her, and their closeness has continued to this day. He's very often busy, and doesn't get as much time to spend with Lilly as he used to, but when they do have time together they are as close as ever, so much so that they could be mistaken for siblings. Darryl is just as teasing but notably less scathing and sarcastic around her, and she often scolds him for his don't care attitude with people, though it doesn't make any difference.
Oz was one of Lilly's high-school friends, the first friend she'd ever made outside of her family, and one of her best. On the surface their friendship seems fairly manipulative, consisting solely of Oz making Lilly do things for him like act in his plays, play mannequin for his dress designs and sing in his shows, and pushing her into situations that make her uncomfortable without asking her opinion on the matter. The truth is that he really does care for her, and would never allow anyone to hurt or take advantage of her, it's just that he's such a bossy, overwhelming personality who likes getting his way, and she's so submissive, that he sees nothing wrong with him taking advantage of things.
Celia is the second friend Lilly's ever made outside of her family, and also one of her best. Though Celia gets along well with anybody socially, she counts only a few people as her real friends. Lilly is one of those, she loves her and would gladly break someone in half if they messed with her. As Oz's closest companion, she often acts as a safe buffer to prevent Oz from overwhelming Lilly or taking too much advantage of her good nature. Lilly has nothing to offer in exchange in terms of physical protection, but supplements by adoring Celia and her confidence and strength, always ready to listen to her or be dragged around for shopping or having her wardrobe reassessed.
Gladstone was one of the many people who came into her shop. He was also one of the many people who inadvertently or otherwise brought trouble into her life. But despite a shaky start where her discomfort at the attention he attracted almost drove him away, Lilly and Gladstone also got on very well, and continued to meet, more so than any of the many people and troubles who blew by the shop on a regular basis. They met again completely by chance, and since that was also chaotic, they decided to meet on purpose. That didn't help matters. Every time they've met has been hectic, confusing and terrifying, and Gladstone has been consistently charming both before and after and often during, and she was very much swept off of her feet.
There's an argument to be made for the fact that she's fallen too hard, too fast, because she's never been in a relationship before, but though she probably concedes your point, she's completely devoted to him and wouldn't have it any other way, even if she often has to chide him for being insensitive or silly at inappropriate moments.
Briar, in her Mother Goose persona, appeared in Lilly's shop uninvited, in a poof of glitter, and claimed she was there to help. And while that was wonderful and very kind of her and everything, the shop was closed at the time, so she did essentially break into the place. Under the very vague suspicion that she might be a villain, Lilly was very polite so as not to upset her, and accepting her offer of book sorting help. Somehow that led to sharing tea a biscuits and somehow that turned into being friends, with outings and visits and gossip and the goose taking a very vested interest in her love life, for better or for worse. Lilly has a surprising amount of patience with Briar's shenanigans, allowing herself to be dragged along with little more than a “Oh Briar.” But she knows the woman's heart is in the right place, and cares for her very much.
Where once there was a rather sweet(?) friendship before the rektcon, and Lilly considered Malicia a friend who was good at heart but just making a long series of bad choices, Malicia is now just 'the nice lady who is good at exorcisms'.