Was it Clara Barton?

A long time ago when I was 7 I went to Clara Barton's house near D.C. I was with my mom, my brother, my godmother, and her boyfriend.

When we got to the house we knocked on the door and a lady came and opened the door. Of course since I was only 7 I could see under the lady's elbow, and while the lady was still holding the door and talking to adults I could see inside the house.

I saw another lady leaning on the wall. I think she was looking at me or at all of us. She had in some kind of dark (greenish, maybe) clothing and I think her hair was black or something of that kind of color.

I only got to see her for a second because the lady at the door moved her elbow and when she moved it back to where I could see into the house, there was no lady there anymore. How could she be there one second and be gone the next I though to myself. So I told my mom what I saw. She told me to tell the tour guide (who was the lady at the door) when the tour was over.

When the tour was over I did tell the tour guide about what I saw, but the tour guide said that there wasn't another woman there. I told the guide that the other woman ran very fast. Then the guide's face changed from ok to scared. She said she'll be right back.

After a little while the guide came back with another woman. She asked me if this was the women I saw. And right off I said no. The woman the guide brought said that she was in the basement the whole time and she didn't even know there were people here.

Was the woman telling the truth? If so, was it Clara Barton? There is a little proof to think it might be Clara.

Clara was in the army, helping out with the wounded, and the lady I saw was in front of the space the guide said Clara kept bandages.

Could it have been my guardian angel? Or it may have not been even anything. If you can help or even better tell me who or what it was I would be grateful.

As for me, I think I did see a ghost and her name is Clara Barton.