I started going to this church because I want to get closer to God. The thing is, there is a girl there I like too, so half of my reason is to get closer to her.

I have a really guilty feeling when I go because I get excited to see her again. At the same time, I am spiritually thirsty for God's love. At worship, I feel spiritually moved, but during the week, all I think about is her.

Am I doing something wrong? I feel guilty.

Liking someone is certainly not wrong. Her being the driving motivation for you attending church is. (not saying that is the reason for you)

If that girl no longer goes to that church.. would you still attend every Sunday and worship God?

Yes, I would still attend.

I would try not to over think it. God's grace is overwhelming and He loves that fact that you're attending church!
Something to also consider is that God is putting her on your heart. If she's a good girl and appealing to you, then maybe God has something planned for you with her.

It is for freedom that Christ has set us free. Stand firm, then, and do not let yourselves be burdened again by a yoke of slavery.
Galatians 5:1
You're free from any guilt or feeling of inadequacy. Don't feel guilty because God loves you no matter what, and nothing you can do can change that for the better or the worse.

All that being said, don't forget why you're at church

I hope it is God's plan.

Thanks for the help!

There is a difference between a desire to pursue someone, and making that person an idol. If you are meeting with Jesus in a real, intimate way, that's good. If you are seeking him above all else, awesome. What becomes an issue is when we associate our relationship with Christ with that person. As a result, we worship them, and not the king of kings.
Seems like you have a good heart. Be in constant prayer over her. Subject yourself to the will of Christ, and pray that he opens doors. However that may look, and PRAISE HIM all the while. Grace is sufficient, God is good, and I speak against any feelings of guilt you may feel, in the name of Jesus.