Bitcoin is transitioning to the epoch where the block reward is small, and the block is at maximum size. As bitcoin enters this epoch, the transaction fees become important for those transactions that are time sensitive. This is part of the original design arc of bitcoin. The transaction backlog has been fluctuating between 4,000 and 50,000 transactions during the past few weeks. As is usual in the bitcoin world, the comments regarding this vary wildly in connection to reality and paranoia content.
You may wish to know the
current backlog and fee recommendations when you submit a payment. As I write this, that recommendation is 160 satoshis / byte for inclusion in the next block. That is the same as 0.00160000 BTC / kb.
The block explorer is showing about 2,000 transactions each block, and about 999 kb for each block, so the system itself is chugging along like a well oiled machine. You are just stuck in traffic while the HOV lane moves past you.
If your user is sophisticated, they can construct a transaction to spend their output from the stuck transaction, and include a large enough fee to sweep both your transaction and theirs into an early confirmation. Actually, anyone who has an output from the transaction can do this. It is difficult to give more detailed commentary without a TxID to review. They probably should not make their first attempt at this on a 25 BTC transaction.