She may not want to give a straight answer because she either does not know what to tell you herself (not having made up her mind) or she wants to see other people as well and not tell you that.
Most important is- what do you want to get out of the situation? Think about that and what future do you see with this relationship and if it is worth your energy and efforts.
The only way to tell if she is being deceitful is to catch her in it or confront her. It is a red flag if you believe that the relationship goes deeper than just friendship and she denies it. It also could be an excuse of not wanting another long term relationship or feeling ready for one. A person usually knows if they want something or not and if they want something will go to an extent to get it.
She may defend you out of guilt of to hide the truth of how things are b/w the two of you. You would only know for sure by asking her and if she gives you an honest answer. otherwise you'd have to speculate.