A girl asked me for but she under age and im taken?

right ive this close friend in another country that i met on holiday like two years ago and we kept in touch via the Wonder's of IM and text, i was surprised to find one year later that she had a crush on me since the holiday and we chatted bout the age difference (im now 18 and she now 14) so i had to decline, and we talked and chatted bout her problems such as her alcohol problem and the fact that she had a babby scare i feel for her and she is like my sister i never had any way now another year past to the presnt day ive gt a beautiful girlfriend that i love but we dont see eachother much , and i was talking to my friend and she sed "oh i miss you so much mate wt say i come to england down ur way we can meet " i sed yer that would be coo we will go swimmin cinimas etc and she replyed "yer and other stuff" unfortunatly im a bit innocent for a 18 year old and asked her wt she ment the she sed you know .. in ur bed i was startled (am still a virgin) my 1st thought was cool .. but then i remembered my gf i love her to much to do that ... i hate cheaters so i sed and in quoat " isnt being my close mate and like the sister i never had enougth..." and she replyed yes but since then we havnt spoken much is there somthing i can say to her to make her a close mate and to let her no i wouldnt o that stuff with her because i lover her but in the differnt way... or do u think that i should wait till she ready to speak agen??