If she is focused on you stronger than a friend would normally be, does little things that are important for you, is always there for you, and doesn’t even try to date anyone else, these are signs that she might be in love with you.
Not everyone is comfortable with this type of direct communication, however, so you can’t assume that just because she hasn’t said anything that her intentions are purely platonic.
Eye contact: This can either be steady, or shy and coquettish. Our pupils will also dilate when we look at someone we like, as the brain is letting more light in so that we can more easily gather information about them. Mirroring behavior: When we are attracted to someone, often we will subconsciously mimic his or her mannerisms or way of speaking. Physical closeness: Usually we prefer people to be at least three feet away from us in social settings. When we like someone, however, the need for this distance diminishes. Posture: We tend to lean in towards people we like, and we’ll often sit or stand with our bodies turned slightly in their direction. We’ll also do things to make our posture more inviting or open, such as uncrossing our knees or arms. Body temperature: Our body temperature tends to increase when we are in the presence of someone whom we’re romantically interested in. We can become flushed and will inadvertently do things to help ourselves cool off. A man might roll up his sleeves or adjust his collar, while a woman may gather her hair away from the nape of her neck. Preening: Women, specifically, will often touch their hair without realizing it. It’s actually a rather primitive impulse; the small movement of lifting the hand to one’s head is enough to draw attention without being obvious. Attention span: Things we are genuinely interested in have the ability to hold our attention for longer spans of time, which is also the case for people we have a special interest in. Touching: Human touch releases a bonding hormone called oxytocin in our brains. When we like someone, we are compelled to touch him or her. Friends will touch each other while having a conversation, but with a romantic interest, the touching is often more frequent and lingering. [1] X Research source
In particular you’ll want to avoid extended eye contact, excessive touching, and physical closeness, as they are usually seen as signs of flirting. On the contrary, pulling away and having a closed pose (like, with your arms folded) suggest that you are not interested.
If you have a preexisting relationship where you interact with each other regularly, such as friends or coworkers, it doesn’t mean you should start ignoring her. Be pleasant, respectful, and responsive, but try to avoid excessive chitchat.
Don’t go into lengthy detail about your interest in other girls. If she does have an interest in you, this could cause her unnecessary emotion pain.
If you do offer this, however, make sure you actually have someone in mind! Don’t suggest it without the intention of following through, as this might further confuse her. [3] X Research source
While it can a difficult conversation to initiate, being honest with her will help her to see the situation for what it is, rather than allowing her to continue stoking the false hope that maybe you feel the same way. [4] X Research source It’s also not necessary to go into details about why you’re not interested. While it’s completely legitimate to not want to date someone because you don’t find them physically attractive, for instance, you don’t need to tell them this. Simply saying “I’m not interested in pursuing a romantic relationship with you” will usually do trick. [5] X Research source Don’t offer an excuse that suggests things might work out between you sometime in the future. If you say something like “I’m still traumatized from my breakup last year”, “I’m just working too much right now to have a relationship”, or “I’m questioning my sexuality”, she might interpret them to mean that you’re potentially interested in her, as well, but the timing isn’t quite right. [6] X Research source
How did their actions make you feel? Were there certain things they did that made the experience worse for you? That made you feel angry, wounded, or embarrassed? Did they say anything that provided you with comfort, despite the emotional pain of rejection?
That said, it’s usually not a good idea to attempt to provide comfort for her, particularly physical comfort. This sort of intimate behavior can be confusing, and might make her feel like she’s receiving mixed messages. It’s also possible that she might ask you to refrain from contacting her for a certain amount of time, the best thing you can do is to honor her request for distance. You may even consider suggesting this if it feels like the emotions are running high. [8] X Research source In the unlikely instance that the emotional response escalates into abusive or self-harming behaviors, however, it’s best to extricate yourself from the situation as quickly as possible. If you are worried about her, contact a friend or family member of hers and ask them to check on her.