Honestly, I don't think going down a yuri route would be a good idea.
I think it would be better and healthier if these two remained just as close friends, as I think that their relationship would be better without romance, and if the bonds between them were connected by it. Not all love is romantic, as they say, and I think it's more thematically relevant to show the different types of connections people have beyond simply familial and romantic in this series and to see how they influence one another.
Teru having a close friendship with another girl were she can just learn to rely on one another I think would be more impactful than immediately turning this into a romance story, which I don't really think is needed here. You have to learn how to stand on your own two feet before you enter a relationship, and I don't think Teru is ready for that.
Also, keep in mind that the reason she trusts her so much is because she reminds her of her sister, and that she's dependable and gives her a shoulder she can lean on. I don't think we're supposed to get the impression that their relationship is meant to be romance-based.