Girls: how long before u lose interest?

There's this girl who I text everyday, most of the time I start the convos, but she always seems into chatting with me, right up till she goes to bed. so I guess we've talked pretty steadily for the last week, and see each other occasionally. she's busy for the next two weeks in another state, so I haven't asked her to hangout sometime...at least not yet. so my question is if u think a girl might be interested in you, how long before she kinda stops losing interest? I just don't want her to quit talking to me or something u know while she's gone, and when she gets back, things be really chill/lame between us.