Hi, I'd like to help you with your question.
It sounds like you are feeling insecure about your relationship. You are upset about your girlfriend's treatment of you when her parents were around and this made you unsure of her feelings for you. Plus you mentioned she has lied to you in the past, making you feel that she may be lying to you again when she tells you that she wants to be with you. Additionally, you feel that since she said she did not have any feelings for you at the beginning of your relationship that she may just be leading you on now.
It is understandable that you are having doubts about how strong your relationship is. It is a very common issue for couples. But you are also looking for signs that your girlfriend doesn't care for you, including considering that she is lying to you. This means that you may be feeling insecure and might be struggling with a low self esteem.
There is no evidence that just because your girlfriend didn't have feelings for you in the beginning of your relationship that she didn't just develop feelings as your relationship progressed. So she is not necessarily lying to you. She just developed feelings for you as she got to know you. Also, she may be feeling overwhelmed with so many issues at once and is trying to sort them all out and that is why she seems a bit different now.
You may want to consider that you are transferring your insecurity onto your relationship. It can become an endless loop if you keep trying to prove to your yourself that your girlfriend wants to be with you and loves you. You will always be able to find some evidence that she does not, even if that evidence is something you think you see.
Instead of focusing on the relationship, you may want to work on how insecure you feel. Insecurity often causes you to feel vulnerable in your relationship and question your status. This creates a rift between you and your partner and things start to deteriorate, the very scenario you wanted to avoid. By finding the root of your insecurity, you can begin to address your problem and take the pressure off your partner and the relationship, and improve your relationship instead.
Learning more about low self esteem and insecurity can help you overcome these feelings. Here are some resources to help you:
The Self-Esteem Workbook by Glenn R. Schiraldi
Ten Days to Self-Esteem by David D. Burns
You can find these books on Amazon.com or your local library may have them for you.
If you feel that self help is not working you may want to consider talking to a counselor. You can find a therapist through your doctor or you can contact your local United Way for the community mental health center near you. They can offer low cost/ no cost therapy based on your income.
I hope this has helped you,