It's important to remember that interpreting someone's response through text messages or social media can be tricky, as tone and context might not be entirely clear. However, in this scenario, a response like "Yes for sure!" with a snap of her laying down smiling on her bed could mean a few different things:
Positive response: Generally, responding with enthusiasm and a smile indicates that she is happy and looking forward to hanging out with you.
Comfortable and relaxed: The fact that she's in a comfortable and relaxed position, like lying on her bed, might suggest that she feels at ease with the idea of hanging out with you.
Interest: Her response and smiley snap could also indicate that she finds the idea of spending time with you appealing.
Casual hangout: Since she's on her bed, it could imply that she perceives the hangout as a casual and comfortable affair.
However, it's essential not to read too much into a single response or message. Context and previous interactions matter, so consider your relationship with the girl and the conversations you've had before making any assumptions.
If you're interested in her and want to see where things might go, the best approach is to proceed with the hangout as planned and be yourself. Pay attention to her reactions and body language during the actual hangout, as that will provide more insight into her feelings and level of interest.
Ultimately, open communication is key in any potential relationship. If you feel comfortable doing so, you can also discuss your feelings and intentions with her at an appropriate time to gain a better understanding of where both of you stand. Respect her boundaries and feelings throughout the process, and remember that relationships often require patience and understanding.