It depends.

If it is a girl who is his friend that the girlfriend is familiar with, it may not be a big deal.

If it is a girl who isn’t his friend that the girlfriend isn’t all too familiar with, she may care.

Also, the frequency in which he does it is important.

The first time he likes another girl’s picture, the girlfriend may be curious.

She may take a look at that girl’s picture and begin to compare herself to that girl.

She may wonder what about this girl’s picture was so enticing.

If it is a sexier photo of a girl, she will care even more.

The first time may make her ask a few questions mentally.

However, if her boyfriend repeatedly likes this particular girl’s pictures or starts liking a number of girl’s pictures, the girlfriend may begin to feel threatened.

Hence, there are a few things you need to look at in order to determine how likely the girlfriend will care.

You have to consider whether this is a girl that the girlfriend is familiar with and knows is her boyfriend’s platonic friend.

Also consider what kind of photo he is liking.

If it is normally a photo with this girl in busy environments where the entire focus isn’t on her physicality but perhaps an activity she may be doing, the girlfriend may care less, as long as the likes aren’t repetitive.

If it is a sexy photo of the girl where she may be posing seductively, the girlfriend may care right from the very beginning.

Hence, it really depends on the circumstances or the manner in which the boyfriend is liking another girl’s picture.

Another reason why a girl would care when her boyfriend likes another girl’s picture is when she may know the girl but she doesn’t necessarily like the girl.

She may not trust this girl at all.

Perhaps she has heard negative accounts about this girl from other people or she has had negative experiences with this particular girl in the past.

If this is the kind of relationship she has with this girl, the girlfriend may be worried about the fact that her boyfriend just liked this girl’s picture.

If this girl has a reputation for being flirty with boys, the girlfriend may become even more concerned.

Also, the stage of the relationship is important.

If it is still very early on in the relationship, a girl would be more susceptible to caring when her relatively new boyfriend likes another girl’s pictures.

At this stage, the relationship is still relatively new and needs more time to become secure.

She may still be worried about outside threats coming into the relationship and jeopardizing it.

She may still be in the process of getting to know this guy better and securing their bond as a partnership.

Thereby, she may feel threatened when he likes another girl’s picture so early in their relationship.

A relationship that has lasted a while is on more solid footing.

A girl would care less at this point, so long as the likes aren’t in rapid succession.