Met a girl through a referral

[Alopolo]

I was recently introduced to a girl through my coworker (who is her sister) by attending a dinner party at her house. There were around 7 people and it was at Lisa's (the girl I'm getting hooked up with) house. As soon as I walked in lisa approached me and gave me a gentle handshake. She is very beautiful, like a 10/10 and way better looking than I expected. So it was a bit intimidating at first but I was then sitting with her on the couch soon and bantering while others were talking among themselves some other part of the house . I think the talking was really good and there was no awkwardness and she would even touch me gently here and there while talking. She also gave me a tour of her house and her comic books collection which I thought was fantastic. When dinnertime came her sister deliberately sat me beside lisa since I was at first hesitating where to sit. During dinner things were good for first few minutes but then I realized she was not making eye contact or being as attentive as before so subsequently I pulled away (not that I was giving her too much attention. I was having a good time and talking and laughing with everyone at the table and didn't single her out with my attention). A couple times she asked me about my interests and such but nothing else came up. Soon after this she explained that she had to attend a girls birthday (who is a far mutual friend of mine). So she left after about a total of 1.5 hours and briefly mentioned to me in front of everyone that "we should go for coffee sometime". I'm not quite sure if she meant that or just said that to make me feel better. When I left the house her sister thanked me for coming and said Lisa was very excited to meet me all week. The biggest problem I found is I never got the chance to get Lisa's phone number.

Now I'm wondering how on earth I should contact her. One way which I want to avoid at all costs is getting her number through my friend. The other is to add her on Facebook and to send a message asking if she is doing anything fun or visiting the art gallery (we both love art) she should let me know and maybe I'll join her and I'll also slip in my phone number. Also not sure on how to go about approaching this girl as most of the time the girls I have met have given me more resistance while this girl was openly asking me to ask her out? Am I wrong? Any suggestions would be much appreciated.

[pcmaster]

I prefer FB. But the way you described her it seems like shes might not be a big chatter on FB. However I say contact her and ask her out in first 5 messages, dont waste too much time chatting but once shes okay to go out with you then, she will chat with you if she likes you.
Also you can use FB to get her phone number as well. Contacting over the phone could be even better.

If you wanna know the secret then she didn't had much resistance because her sister knows you and girls are much easier when you have mutual friends who introduce you. So yeah you didn't start from zero here, you already know her sis and she helped.

[Alopolo]

Wow it's impressive that you knew she doesn't use Facebook much. So that leaves me with only option of email. That's the only contact info I have. I think it would be awkward to get her number without her knowing. I rather get the number myself because that will tell me a lot about how she feels about me.