No, she can rent it to others and use those proceeds to pay for her expenses elsewhere, if she wants, but she cannot effectively pledge the ownership to anyone as security.
A life estate is an ownership interest that lasts for the life of the specified life tenant (or sometimes for the life of someone else). As such, it is not particularly valuable as a collateral asset in foreclosure because the lender could not "sell" it to recoup its unpaid loan, and the life tenant has no power to grant that which is not hers.
For the others answering "she doesn't own it", you're simply wrong. Look it up. She owns it until she dies. That's what life estate means. It has absolutely NOTHING to do with whether she actually lives there, other than the fact that, as the owner, she may certainly choose to.