NARA has compiled military service records from the Black Hawk War (and all other wars).It is possible that the widow may have been pensioned, in which case NARA would also have the pension file.
The widow never received land, she received a bounty land warrant certificate for her husband's service.This was a fancy document that could be exchanged for a piece of land, or sold for cash.Most soldiers/widows stayed put and sold the warrants to other people who desired to move west.The person that the widow sold the warrant to chose land in Illinois and used the bounty land warrant to obtain the land patent.
If the soldier/widow was pensioned, the bounty land warrant application papers would probably be filed in with the pension.If neither were pensioned, then there would be a separate bounty land file at NARA.Since this warrant that you mention was for 40 acres under the act of 1850, there will probably be another one for 120 acres under the act of 1855. The pension and/or bounty land warrant application file would have personal information, including the date of marriage and the widow's maiden name, among other things.
NARA would have the actual surrendered warrant certificates that can also be copied.They are not very informative, but they are colorful documents.