I was still married to my husband when he died but his daughter from his previous marrage depleted his pension. was I entitled to it or was she?

Its hard to answer because you have indicated "I was still married".  This seems to indicate that there was something happening, whether you had filed for divorce, or were separated, or something else.  As his wife, you were entitled to his pension account.  however, if he had previously been divorced, he might have named his daughter on that account between the time he was divorced, and when he married you and then the daughter was named as a beneficiary.  the pension administrator may not have had any information about a new marriage, saw that her name was on the account as beneficiary, and released the money to her.  You need to contact the pension administrator and find out what happened.